Grunt: The Curious Science of Humans at War

11. OLD CHUM How to Make and Test Shark Repellent

IF YOU WERE IN the market for a chemical that is harmless to humans but toxic to lesser classes of creature, you might reach out to someone in agriculture. A good pesticide, if there can be such a thing, combines both qualities. The insecticide rotenone was the topic of a 1942 memo from the US Department of Agriculture to the US Eleventh Naval District. In addition to killing bugs, rotenone, the letter stated, is a powerful fish poison. When added to water at concentrations only feebly toxic to humans, the chemical “stupefied goldfish.”

This was encouraging information, except that the Navy had inquired about something for sharks. World War II marked the first time in US military history that battles were being fought on and over tropical seas, and stories had begun to circulate of sailors and fliers being attacked and devoured after abandoning ship or ditching their plane. (During the previous world war, crews wound up in the North Atlantic, where cold devoured them first.) One particular narrative made its way to a man named Henry Field (as in the Field Museum of Natural History), who at the time held the title Anthropologist to the President, as well as a post with—well, hello again!—the OSS.

In June 1941, the story went, an Ecuadorian Navy plane went down in the Pacific after running out of fuel. The “desperation and terrification” of the flight officer is detailed in the official report of the incident, which Henry Field either heard about or read. It was a moonlit night. The man wore a life jacket, and as he swam he pushed along the body of a drowned colonel. Sharks began to cross the water in front of him. “At a given moment I felt that they were trying to take away the corpse, pulling it by the feet, on account of which I clutched desperately the body of my companion and together with him we slid until the tension disappeared.” Here I confess I became more interested in the translator of the report than its terrificated protagonist: “Once refloated, with despair I touched his legs and became aware that a part of them was lacking.” The flight officer abandoned the demi-corpse and continued alone to shore, “with various sharks following.”

“Night after night,” Henry Field recalls in his memoir, “I thought of these men… with sharks cutting through the water around them.” As Anthropologist to the President, he had Franklin Delano Roosevelt’s ear, even, it seemed, in matters of ichthyology. “I wrote the president a memorandum suggesting that we try to develop a shark repellent.”

With presidential blessings, Field met with fellow museum curator Harold J. Coolidge, also on the payroll of the OSS. Coolidge was a primatologist—a silverback gorilla he collected (shot) in the Congo resides to this day in Harvard University’s Museum of Comparative Zoology—but he agreed to oversee the shark project. You can well imagine that a gorilla expert on salary with a spy organization might suffer a mild sense of purposelessness. Here at last was something up his alley, if not precisely on his doorstep. Coolidge hired another curator pal, W. Douglas Burden, as the project’s principal investigator. Burden was an expert on Komodo dragons, had written an entire book about Komodo dragons, but he, too, knew little about sharks.

For actual shark expertise, the OSS turned to a college dropout named Stewart Springer, whose résumé included stints as a commercial fisherman and as a chemical technician at the Indianapolis Activated Sludge Plant. In 1942, there were no experts in shark biology and behavior. Truly, no one knew much about the creatures. The combination of hands-on shark experience and sludge chemistry was, in fact, ideal background for the task. “Dr.” Springer, as some of the OSS correspondence refers to him, was as good as it got.

The US Navy agreed to contribute funding, even though, as one of their rank pointed out, there was at that time no formal record of anyone who had taken the oath of the Navy having been harmed by sharks. Their concern was morale. Fear of sharks, however irrational, was thinning the ranks of willing fliers. Stewart Springer voiced the cockamamie irony of it: “It was okay to give one’s life for one’s country, but to get eaten for it was another matter.” If nothing else, a repellent would serve as what Douglas Burden called a “pink pill,” a psychological fix for shark-shy aviators. On July 3, 1942, funding was approved for OSS Office of Scientific Research and Development Project 374, Contract OEMcmr-184: a three-month investigation “looking to the development of means of protection against sharks, barracuda and jellyfish[50] for men adrift in lifebelts.” (In three hundred some pages of archived correspondence for Project 374, I saw but two passing references to barracudas. As far as I can tell, no one ever got around to jellyfish.)

The lab work was done mainly at Woods Hole Oceanographic Institution, which housed a collection of captive sharks called dogfish—in size and temperament, somewhere between a great white and a goldfish. Rotenone was among the first substances the team tested. “Definitively negative,” Burden reported to Coolidge. “Lethal doses do not deter the feeding process.” The shark would die, but not before you did. Until such time as goldfish presented a threat to national security, rotenone would be limited to the arsenal of the USDA.

Seventy-nine substances were tested and rejected. Irritants failed. “Repulsive odors” failed. As did clove oil, vanillin, pine oil, creosote, nicotine. They tried compounds related to mothballs, asparagus, horse piss. The sharks ignored all of it. The first “hot lead” sprang from an item of sharker lore. Springer had heard that a shark carcass abandoned on a bait line will ruin the spot for shark fishing. He and his team got to work. They rented an “isolated” house in Florida for $10 a month, and never, I’m guessing, was a cleaning deposit more roundly withheld. Chunks of shark muscle tissue were left out at room temperature for four or five days. An extract was then prepared by grinding the decomposed flesh, stirring in alcohol, and filtering the resultant shark muck.

Forty-three experiments later, Springer enthused in a note to Burden, it was possible “to say POSITIVELY that the meat contains some substance strongly repellent to sharks.” Repellence value 88.4 percent! Ninety to 100 percent effective! The bimonthly progress report of Contract OEMcmr-184 describes Springer as “sufficiently convinced of the effectiveness of the concentrate that he would be willing to test it in a life belt with a bucket of blood.”

An expedition to test the decayed meat concentrate on wild sharks had been slated as the next step, but Springer and Burden urged the OSS to begin production immediately. “If we really have something now and… the field test delays use of a good thing by six months,” Springer wrote to Coolidge, “and if during those six months… some poor devils might have been protected it would be bad.” Springer happened to know a contractor who could get right to work producing the concentrate. Shark Industries was a Florida purveyor of shark skins and shark oil—and also, speaking of things that smell fishy, Springer’s sometime employer. The company, Springer felt certain, would be able to produce enough shark extract to outfit 2,000 to 5,000 life jackets per month. If Springer had his way, the whole undertaking would soon be moot, as there would be no sharks left to repel.

The OSS didn’t bite. Rather than move forward with the concentrate, they wanted to try to isolate the active ingredient—a compound that could be ordered or cheaply synthesized, thereby saving them the cost and bother of large-scale shark carcass reduction. Chemists were hired, three of them, and they soon came up with a promising candidate: ammonium acetate. It, along with two compounds that had earlier shown promise (copper sulfate and maleic acid), plus thirty pounds of the Macbethian-sounding “extract of decomposing shark meat,” were flown down to Ecuador, to the very same waters where our story began, to be tested on “voracious surface-feeding sharks.” Lodgings were secured, boats and guides hired. Three weeks later, Burden dispatched a glum cable: “The waters off the coast of Ecuador have been virtually empty.”

From deep in the pockets of the OSS came Harold Coolidge’s reply: Try Peru. “Don’t be discouraged,” he wrote. “Shark hunting is not unlike tiger hunting. You remember how plentiful tigers are in various parts of French Indo-China until you reach the point when you want to shoot one and have only two or three weeks at your disposal.” You got the sense, leafing through these letters, that a career in natural history was little more than a way for well-connected gentlemen to finance far-flung safaris and fishing expeditions in the name of science. The title of Douglas Burden’s memoir nicely summed the job: Hunting in Many Lands.

The expedition eventually located some sharks, off the coast of Guayaquil, Ecuador. More discouraging words followed. Nothing worked. They tried combining the ammonium acetate and the copper sulfate, and that compound (copper acetate) seemed effective. Unfortunately, two or three pounds of it, in the form of a slowly dissolving cake (think urinal, not birthday), would be needed for one day’s protection. This would not do. The Navy wanted something small enough and light enough—six ounces at most—to seal in a packet and attach to a life belt. The life belt, a precursor to the flotation vest, was a deflated rubber tube worn around the waist at all times and inflated in an emergency. Like any part of a serviceman’s uniform, the belts developed holes from wear and tear. The last thing a seaman needed on top of a leaky life belt was a three-pound anchor of questionably effective shark repellent.

The Navy was losing patience. A hundred thousand dollars—$1.5 million in today’s currency—had been spent, and they were no closer to having a practical, effective shark repellent than they’d been a year ago. The OSS was edged out, and the project taken over by the Office of Naval Research and the Naval Research Laboratory (NRL). The first thing the Navy did was to make the field tests more realistic. Springer and Burden had been baiting lone meandering specimens—“casual sharks”—using hunks of mullet as their man-in-life-belt stand-ins. The NRL wanted a better approximation of the thrashing aftermath of a downed ship or plane and the “large schools of frenzied sharks” that that scenario was thought to attract and inspire. The so-called feeding frenzy was a state of mind in which, it was speculated, olfaction took a back seat to the “mob impulse.” In August 1943, copper acetate was brought on board a shrimp trawler off Biloxi, Mississippi, and tested for its ability to protect “trash fish”—flailing, panicked specimens tossed off the back because they weren’t shrimp. Guess what? Even five to six pounds of copper acetate per bushel of trash fish “did not by any means” interrupt the het-up mob trailing the boat. “The sharks hardly paused.”

The final slap in the face of Project 374 would come in the form of a paper by Navy Captain H. David Baldridge Jr.: “Analytic Indication of the Impracticability of Incapacitating an Attacking Shark by Exposure to Waterborne Drugs.” By plotting the speed of a closing shark against the speed of dilution and the concentration needed to put the creature out of commission, Baldridge showed that such a large quantity of drug would be needed that it “does not appear to be at all reasonable as an approach to the control of predaceous shark behavior.” As one of Burden’s colleagues put it: “You can’t do much with a pint of liquid in an ocean.”

Taking a cue from the octopus, Navy researchers next looked into using clouds of inky dye as a way to hide crewmen from potential predators. Under those same “mob psychology” conditions, all feeding activity was stopped until the dye had diluted to the point at which it no longer obscured the prey. Production began at once. Shark Chaser’s active ingredients: 80 percent black dye and 20 percent pink pill—a little copper acetate having been added to the pot[51] for some false peace of mind. From 1945 all the way through to the Vietnam War, packets were available for the emergency survival supplies of lifeboats, life rafts, and life jackets on military vessels and planes. Even the post-splashdown survival kits of the Mercury astronauts were stocked with Shark Chaser.

Through all of it, there’d been skeptics among the Navy brass. Rear Admiral Ross T. McIntire, Chief of the Navy’s Bureau of Medicine and Surgery, made the eminently reasonable point that a package labeled SHARK CHASER in bold capital letters might in fact lower, not raise, morale, planting, as it would, the seed of terror in minds that had been, until that moment, occupied by the real threats of ocean survival: dehydration, starvation, drowning, heat, cold. Especially given the “negligible danger,” to use McIntire’s words, that sharks posed to Navy personnel.

How negligible? Opinions varied, but at one point in the proceedings, the Commander of the South Pacific Fleet issued a memo to all naval bases and hospital ships soliciting “authentic cases of injury to personnel from attack by sharks.” With all hands reporting, the final count was two cases. (One additional attack was later determined to have been a “vicious eel.”) The OSS responded in time-honored intelligence-agency style: They disappeared the report. “The report on shark attacks has been destroyed, as you requested,” reads an interoffice memo to Harold Coolidge from a staffer in December 1943.

It was another stink bomb for the OSS. They’d set out to develop a shark repellent based on one man’s experience and another’s political connections, with no solid data to support a need. If you look back at the Ecuador incident—the original impetus for all this—it really wasn’t a testament to the danger or ferocity of sharks. If anything, it was a testament to the disinterest and/or shyness of sharks. The flight officer was adrift in a life jacket for thirty-one hours, yet he emerged from the ocean unmauled by the retinue of sharks that followed him most of the way to shore.

If you wanted to preserve morale, the better approach would have been to share these reassuring facts and statistics. “Correct information,” wrote McIntire, “would be more universally operative in alleviating those fears than any repellent that could be devised.” Beginning in 1944, that is what the Navy did. Their Aviation Training Division distributed copies of a pamphlet called Shark Sense to all future fliers: 22 pages of comforting facts, illustrated with comic drawings of cringing, perspiring, fleeing (“HALP!”) sharks.

And it proved true. In a review of 2,500 aviators’ accounts of survival at sea during World War II, there were just 38 shark sightings, only 12 of which resulted in injuries or death.

As reassuring as it was, Shark Sense failed to address the most urgent questions on the minds of men afloat in the bedlam of a disaster at sea. Is it true that a shark can smell a drop of human blood in an ocean of seawater? Does noise arouse a shark’s curiosity, or scare it away? What about movement? Some accounts—including that of the swimming Ecuadorian—indicated that thrashing scared a shark away; others suggested it sparked their interest. No one really knew.

In 1958, the head of the Biology Branch of the Office of Naval Research, Sidney R. Galler, set out in pursuit of answers. He funded a shark research panel (the Shark Research Panel) and helped establish the Shark Attack File, a database of global incidents that continues today as the International Shark Attack File. David Baldridge’s statistical analysis of nine years of Shark Attack File data gave the world—I’m quoting a 2013 National Marine Fisheries Service paper here—“most of what we know today about shark attacks.” Much of the rest comes from studies the Office of Naval Research funded in the 1950s on shark predation, olfaction, and feeding behavior. “If you had a good idea for research on sharks,” Baldridge told the author of a historical account of shark research, published in Marine Fisheries Review, “you went to Sid.”

ALBERT L. Tester went to Sid. He had a good idea, he had three species of shark in the ocean outside his door, and he had a pair of fifty-foot-long seawater tanks for experimenting. Tester worked at the Eniwetok Marine Biological Laboratory in the Marshall Islands. (Eniwetok was one of the atolls, along with Bikini,[52] upon which the US had tested nuclear bombs; the lab provided data on the effects of radioactive fallout on sea life—and, if anyone tracked the obituary pages over the ensuing decades, Eniwetok staff.) Tester set out to determine what, specifically, draws a shark to its prey. Do sharks hunt mainly by sight or smell? If it’s smell, which smells? Whose smells? If repelling sharks wasn’t a reasonable option, a sailor or aviator’s best bet was not attracting them in the first place.

Let’s start with the good news. Human urine does not attract sharks. When presented with anywhere from a half teaspoon to a third of a cup, blacktip sharks in Tester’s tanks took no interest. Neither excited nor repelled, the sharks simply noted the substance, as evinced by a quick turn, or “swirl,” which is, I guess, how one acknowledges pee in the pool when one has no eyebrows to raise or shoulders to shrug.

Human perspiration is likewise uninteresting to the shark. It was sufficiently hot and humid in the shark house that Tester and his grad students were able to collect what they needed by sponging each other’s bodies and wringing the sponge into a bucket of seawater that was then quietly siphoned into the shark tank. In general, the sharks, and who can blame them, were mildly put off. The perspiration of Albert L. Tester was particularly repulsive to them. At concentrations as low as one part per million, Tester’s sweat caused a captive blacktip shark to shake its head and make “a rapid exit from the area.”

All-over body sweat—the cooling waters of the eccrine glands—is different from flop sweat. Had Tester done what my friends at the Monell Chemical Senses Center did to me—gathered the pungent armpit exudations of a human under stress—his results might have been different. The sharks might have detected the scent of distress, of easy pickings, and gone into attack mode.

That is precisely what happens when a shark’s preferred prey falls under stress. The shark senses a no-hassle meal and closes in to attack. Tester harassed a bucket of groupers by “threatening them with a moving stick” (elsewhere referenced as “poking”). Pumping water from the bucket—scientific nomenclature: “distressed grouper water”—into the shark tank provoked a “violent hunting response.” Since the prey were outside the tank, we know it wasn’t the sight or sound of grouper pandemonium that set off the sharks’ predatory moves. It had to be some chemical exuded through the groupers’ skin or gills. And not just any grouper scent would do the trick. When “quiescent grouper water” was introduced into the tank, the sharks paid little heed.

Fish blood and fish guts—two blaring sensory trumpeters of piscine distress—also trigger vigorous hunting moves. So powerful is the chemical signal, Baldridge found, that sharks could be roused to devour a rat—not normally an item of gustatory interest—if its fur were coated with “mullet blend” (whole mullets blenderized with a little water). In a different study, sharks were inspired to attack a kitchen sponge that had been dipped in a bowl of fish body fluids. “Sharks,” wrote Baldridge, “will strike essentially anything that has been treated with fish ‘juice.’”

That includes spearfishers. In particular peril are those who swim around with the day’s catch hanging from their belts or trailing from lines. At the time Baldridge ran his analysis, the Shark Attack File had logged 225 incidents that mentioned the presence of wounded fish and/or fish blood or guts. “Sharks,” marveled Tester, “are able to track down and converge on a distressed fish (such as a live fish suspended from a hook through the jawbone but otherwise uninjured) with uncanny speed and accuracy.”

Spearfishing probably serves to explain why 17 percent of the Shark Attack File victims were wearing wetsuits. The original theory put forth was that the sharks mistook people in black wetsuits for seals. Perhaps that happens too, but where spearfishing was involved, it’s more likely that the wetsuit’s accessories—the spear and the belt of oozing fish—drew the shark.

Dead fish also ring the dinner bell. Tester exposed blacktip and gray sharks to a sushi bar of fish flesh: tuna, eel, grouper, snapper, parrot fish, giant clam, octopus, squid, and lobster. All of them he classed as attractants. Sharks prefer to take no risks. They prefer to go after a meal that’s not going to put up a fight. Injured is good. Dead is better.

Which makes you wonder about the alleged shark-repellent qualities of decomposed shark flesh. Tester wondered, too. He secured some “alleged shark repellent” from a fisherman, another sample from a fisheries lab, and a sample his team prepared on their own by leaving hammerhead and tiger shark flesh outside in the tropical heat for a week. No repellent effects were observed. On the contrary, it sometimes functioned as an attractant. “Our results… seem to be at variance with those of Springer…. No convincing explanation can be made.” Tester perhaps unaware of the powerful attractant effect of kickbacks from shark-processing plants.

As with fish, so with humans. Over and over, in the shark attack reports of World War II, corpses took the hit. A floating sailor could dispatch a curious shark by hitting it or churning the water with his legs. (Baldridge observed that even a kick to a shark’s nose from the rear leg of a swimming rat was enough to cause a “startled response and rapid departure from the vicinity.”) “The sharks were going after dead men,” said a survivor quoted in a popular book about the 1945 sinking of the USS Indianapolis, an event that often comes up in discussions of military shark attacks. “Honestly, in the entire 110 hours I was in the water,” recalls Navy Captain Lewis L. Haynes, in an oral history conducted by the US Navy Bureau of Medicine and Surgery, “I did not see a man attacked by a shark….” They seemed to have been, he said, “satisfied with the dead.” Haynes says fifty-six mutilated bodies were recovered, but there’s nothing to suggest that any more than a few of them were bitten into while alive.

Why, then, do sharks hang around life rafts? For what’s underneath. Schools of fish loiter there, either for the shade or to feed on smaller marine life that gathers to take the shade on the raft’s underside. Recalled one World War II sailor: “Larger fish came to feed on those minnows, then larger ones to get them; finally the boys with the peculiar dorsal fins arrived to see what the fuss was about.” Here’s one more, just because I like it: “The shark submerged and swam directly under the raft…. We all sat very quiet,… and the radar man abandoned the idea of defecating over the side for fear of capsizing. The shark repeated this behavior several times but at no time seemed concerned with us.”

And so it continues to be. I know of only one recorded instance in recent history of a shark’s biting Navy personnel. In 2009, a bull shark took off the hand and foot—in one bite—of an Australian clearance diver during a counter-terrorism exercise in Sydney Harbor. I asked Naval Special Warfare Command communications specialist Joe Kane about sharks attacking Navy SEALs. “You’re coming at this the wrong way,” he said. “The question is not, Do Navy SEALs need shark repellent? The question is, Do sharks need Navy SEAL repellent?”

The modern US Navy has no formal shark-attack curriculum. One diver recalls being told to descend slowly and take cover on the bottom should he sense a threat. A 1964 Air Force training film called Shark Defense advises downed aviators to blow a stream of bubbles or yell into the water. I asked veteran shark videographer Robert Cantrell what he thought of this advice. Cantrell has swum among sharks, cageless, for three decades. This is a man who will apply the adjective “nippy” to a group of excited blue sharks. His answer, an answer Baldridge and Tester often came up with, is that it depends on the kind of shark. Screaming into the water may briefly deflect a bull shark, Cantrell notes, but not a tiger shark. Bubbles scare blue sharks, but other species ignore them.

The last Air Force suggestion was a puzzler: “Tearing up paper into small pieces and scattering them all around.” I suppose it was meant as a means of distracting the shark—or maybe just the sailor, now absorbed in the challenge of locating sheets of paper while afloat at sea. On one of Cantrell’s expeditions, he threw some stale bagels overboard. Tiger sharks swam over immediately; bull sharks ignored them. Cantrell’s main advice to the diver who encounters a shark? “Enjoy the experience.”

Let us turn now to the question on many a sailor’s mind: Is it true that human blood draws sharks? The results of Baldridge’s and Tester’s experiments are inconsistent. Sometimes the sharks behaved as though attracted to the blood; other times they avoided the test area. Tester wondered whether the freshness of the blood was a factor. In his own experiments, blacktip sharks and greys were strongly attracted to blood less than one or two days old—at concentrations as weak as .01 parts per million of seawater. But Baldridge’s analysis of the Shark Attack File data belie this finding. In only 19 of 1,115 cases was the victim bleeding at the time of the attack. “It is difficult,” he concluded, “to accept the concept that human blood is highly attractive and exciting to sharks in general when so many shark attack victims have been struck a single blow and then left without further assault even though they were then bleeding profusely from massive wounds.”

In Baldridge’s own tests, he presented four species of shark with the novel menu option of a swimming, bleeding lab rat. As fellow mammals, rats should possess blood that’s about as enticing (or unenticing) to a shark as our own. As he expected, the sharks showed no interest.

The bottom line is that the preponderance of shark attacks, like most animal attacks, are prey-specific. If you don’t look or smell like dinner, you are unlikely to be so treated. Predators are attuned to the scents of creatures they most want to eat. Sharks don’t relish human meat. Even though a shark can detect human blood, it has—unless starving—no motive for tracking it to its source.

That fact should be reassuring to women who enjoy swimming in the ocean but worry about doing so during their periods. But menstrual blood is different, in a uniquely shark-worrisome way. If you’ll permit it, a brief shore leave; the US Navy of the 1960s was not interested in menstruating women. The National Park Service, however, was. In 1967, two women, at least one of them menstruating, were killed by grizzly bears in Glacier National Park. Conjecture arose that it had been the blood that inspired the attack. Wildlife biologists didn’t buy it, and one of them, Bruce Cushing (delightfully mis-cited in subsequent bear attack/menstruation research as Bruce Gushing), set out to collect some data. Cushing opted to study polar bears, because they feed almost exclusively on seals, yielding a clean baseline with which to compare the animals’ zeal for menstruating women.

If you put seal blubber in a fan box and aim the aroma at the cage of a wild polar bear, that bear will exhibit what Cushing called “maximal behavioral response.” It will lift its head and sniff the air. It will begin salivating heavily. It will get up and pace. It will chuff. It will groan. Only one other item that Cushing placed in the fan box could make a polar bear groan: a used tampon. Chicken didn’t do the trick, nor horse manure, musk, or an unused tampon. Coming in a close second: menstruating women. The women weren’t in the fan box, but in a chair facing the polar bear cage, where they “sat passively,” perhaps marveling at the strangeness of life on Earth. Cushing also tested ordinary blood, drawn from people’s veins; this elicited no response whatsoever from any of the four participating bears.

In other words, it isn’t the blood that makes a tampon attractive to polar bears. It’s something uniquely… vaginal. Some kind of secretions that, please forgive me, smell like seals. This makes sense, does it not? When a feminine hygiene company hires a lab to test the efficacy of a scented menstrual product, the standardized odor employed for this purpose is known as a “fishy amine.”

So alluring is the intensely vaginal/sealy scent of a tampon that a polar bear seems not to notice that it does not also taste like seal. In 42 of 52 instances, a wild polar bear who encountered a used tampon affixed to the top of a stake (scientific nomenclature: “used tampon stake”) ate or “vigorously chewed” it. Only seal meat was more consistently pulled from the stake and consumed. Paper towels soaked with regular blood—here again, nailed to a stake like a skull warning foolhardy jungle explorers—were eaten just three times.

What does this tell us about sharks? Should women be worried? Hard to say. How crazy are sharks for seal meat? Do dead groupers smell like used tampons? Unknown. I’d stay in my deck chair, if I were menstruating you.

Cushing concluded his paper by suggesting that since polar bears enjoy used tampons, there was a strong possibility other ursids would, too. But bears, like sharks, vary by species. Forest bears aren’t connoisseurs of stinky marine life as polar bears are. Grizzlies like salmon, but they take them fresh. Black bears forage for garbage, so who knows what they’ve come to develop a taste for over the years.

To settle the matter, here comes the US Forest Service. Had you been off-loading garbage at a certain Minnesota dump on August 11, 1988, you would have been witness to an arresting sight. “We tied… [used] tampons to a monofilament line and spin-cast them to foraging bears,” wrote Lynn Rogers and two colleagues at the North Central Forest Experiment Station. Despite some fine fly-casting chops on show—the bait being “cast past the bears and dragged back under their noses”—20 out of 22 tampons were ignored. Such was also the fate of used tampons proffered “by hand” to black bears that frequented—though perhaps not anymore—an experimental feeding station. Also ignored: five used tampons tied together and thrown at a group of black bears, as well as all but one of a tasting flight of sodden tampons placed in the middle of a bear trail—four soaked with menstrual blood, one with nonmenstrual blood, and one with rendered beef fat. Ten out of eleven bears “swept their noses closely over the group, ate the tampon containing beef fat, and walked on.”

All in all, a resounding testament to the safety of national forests, and the patience of black bears.

FRANK GOLDEN was an authority on the things that happen to a human body immersed for any length of time in cold seawater. Golden—a physician who, by his own description, “swam like a stone”—researched the topic for the Royal Navy Air Medical School during the late 1960s and early 1970s. The text headings in Golden’s classic Essentials of Sea Survival provide a menu of horrors awaiting service members or anyone else forced to abandon ship or ditch a plane over water: Cold-Shock Response, Breath-Hold Time Reduction, Swim Failure, Drowning, Secondary Drowning, Saltwater Ulcers, Hydrocution, Trapped Under Ice, Severe Hypothermia, Oil Contamination, Immersion Foot, Turtle Blood,[53] Sunburn, Wave Splash, Osmotic Diarrhea, Rescue Collapse, Rewarming Collapse. There is no heading for Shark Attack. Sharks don’t even make the index.

To a sailor whose sunken craft is a submarine, all of this, the myriad dangers and discomforts of the ocean’s surface, are a distant fond dream.