In February 2006, Robert Hewitt was scuba diving near Mana Island, off the coast of New Zealand\u2019s North Island. Hewitt was an experienced navy diving instructor with 20 years in the service, and he told his dive buddy that he would swim back to shore himself. Instead, when he next surfaced, he had been pulled several hundred meters away by a strong current. The dive boat had moved on, and Hewitt was left alone, the tide pushing him farther and farther from shore.<\/p>\n
In a recent issue<\/a> of the journal Diving and Hyperbaric Medicine<\/em>, a team of researchers led by physiologist Heather Massey of the University of Portsmouth in the UK take a closer look at what happened next: Hewitt\u2019s progressive deterioration over the next four days and three nights, how he survived, and what took place after his eventual rescue. It\u2019s an interesting glimpse at a branch of extreme physiology that most of us hope we\u2019ll never encounter.<\/p>\n (Massey\u2019s interest isn\u2019t purely theoretical. She\u2019s currently training to swim across the English Channel, which will require prolonged immersion in cool water. She also took home a gold medal<\/a> from the World Ice Swimming Championships last year, in temperatures just a few degrees above freezing, and helped British open-water swimmers<\/a> prepare for the Rio Olympics.)<\/p>\n The most pressing challenge facing Hewitt was the water temperature of 61 to 63 degrees Fahrenheit (16 to 17 degrees Celsius), well below body temperature. According to physiological models, when water is 59 degrees Fahrenheit (15 degrees Celsius), the median survival time is between 4.8 and 7.7 hours. Amazingly, Hewitt spent the next 75 hours in the water, drifting back and forth over a distance of nearly 40 miles before he was spotted by Navy diving friends and rescued.<\/p>\n In general, immersion in cold water produces a four-stage response. First is the \u201ccold shock response\u201d that triggers \u201can inspiratory gasp, uncontrollable hyperventilation, hypertension, and increased cardiac workload.\u201d If you\u2019re not ready for it, this shock response can cause you to inhale water and drown and can set off heart arrhythmias. Hewitt had two key defenses against the cold shock: a five-millimeter custom-fit wetsuit and habituation from more than 1,000 previous dives, which eventually blunts the initial shock response.<\/p>\n After the cold shock, which peaks within 30 seconds and diminishes after a few minutes, the next stage of immersion is peripheral muscle cooling. For every 1.8 degrees Fahrenheit (1 degree Celsius) that your muscles cool, your maximum muscle power drops by about 3 percent. That means you can lose the ability to swim before your core actually gets hypothermic. Hewitt did indeed lose the ability to swim at some points during his ordeal\u2014sometimes because he lost consciousness\u2014but he had a buoyancy compensator that kept him floating with his head above water.<\/p>\n The third stage is deep body cooling, which affects both physical and mental function and eventually results in loss of consciousness and then death. No one took Hewitt\u2019s temperature until he had been wrapped in blankets and received warm drinks after his rescue. At that point, it was 96.3 degrees Fahrenheit (35.7 degrees Celsius), which isn\u2019t particularly low. He did have some episodes of confusion and disorientation that suggest he was on the border of hypothermia, but it\u2019s hard to be sure.<\/p>\n For every 1.8 degrees Fahrenheit (1 degree Celsius) that your muscles cool, your maximum muscle power drops by about 3 percent. That means you can lose the ability to swim before your core actually gets hypothermic.<\/p><\/blockquote><\/div>\n One key factor that helped stave off hypothermia was the fact that Hewitt is (in the words of the researchers) \u201ca large, muscular male\u201d; at 5'11″ and 220 pounds, he clearly had a decent amount of insulation. In fact, for every 1 percent increase in body fat, you slow your rate of heat loss by 0.18 degrees Fahrenheit (0.1 degree Celsius) per hour\u2014a big deal when you extrapolate to 75 hours. Hewitt also tried to maintain the fetal position, which minimizes heat loss and extends survival time in cool water.<\/p>\n The fourth and final stage of immersion, if you make it that far, is the \u201ccircum-rescue\u201d phase. It\u2019s apparently quite common for people to collapse during rescue, thanks in part to the change in pressure when you leave the water and the strong nervous system reaction to the idea of being rescued. With this in mind, Hewitt\u2019s rescuers kept him horizontal to maintain blood flow to the brain and gave him \u201cverbal encouragement\u201d to keep fighting for his life.<\/p>\n Of course, cold water wasn\u2019t the only challenge in play. Despite water, water, everywhere, dehydration is a serious problem\u2014in fact, the squeeze of the wetsuit and water pressure shunt blood to your core, which stimulates urination, even when you\u2019re already dehydrated. The practical guidance in situations like this is that you should avoid drinking for the first day; this will trigger hormone changes that make your body start conserving water. After that, aim to scrounge up half a liter per day. Hewitt used his mask and wetsuit jacket to collect rainwater, but this was far below his needs. When he was rescued, he drank a liter and a half of water, then received another six liters intravenously.<\/p>\n Prolonged soaking in seawater, along with the friction from his wetsuit and fins, damaged Hewitt\u2019s skin pretty badly. When found (put your spoon down for a moment), \u201chis body was covered with sea lice feeding on his macerated skin.\u201d And then there\u2019s the psychological challenge, both during and after the ordeal. By the third day, he was contemplating (and half-heartedly attempting) suicide, but he managed to keep fighting.<\/p>\n Can we extract any lessons from Hewitt\u2019s ordeal? Well, wearing a wetsuit and weighing more than 200 pounds obviously helped, but those aren\u2019t particularly useful takeaways. Staying in the fetal position\u2014sometimes known as the \u201cheat escape lessening posture,\u201d or HELP\u2014was a good idea. Ultimately, the most pointed lesson, and the one Hewitt himself now spreads as a water safety advocate, is that he shouldn\u2019t have been in that situation in the first place. Rather than diving alone, he should have aborted the dive and joined another group or, at the very least, used a surface-marker buoy to flag his position. \u201cIn some ways, Rob almost contributed to his own demise,\u201d the police search team leader said bluntly. \u201cHe took some shortcuts.\u201d<\/p>\n Still, shit sometimes happens. And if it does, the other big lesson to keep in mind is that in defiance of all the physiological models, Rob Hewitt survived for an astounding 75 hours alone in the cold water. If you find yourself out there, don\u2019t give up.<\/p>\n Discuss this post on <\/em>Twitter<\/em><\/a> or<\/em> <\/em>Facebook<\/em><\/a>, sign up for the Sweat Science <\/em>email newsletter<\/em><\/a>, and check out my forthcoming book, <\/em>Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance<\/a>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":" In February 2006, Robert Hewitt was scuba diving near Mana Island, off the coast of New Zealand’s North Island. Hewitt was an experienced navy diving instructor with 20 years in the service, and he told his dive buddy that he would swim back to shore himself.<\/p>\n","protected":false},"author":44696,"featured_media":2275321,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"uuid":"b272c17d7d4a8e0c80c8eb2cf3e9aa3c","footnotes":""},"categories":[2545],"tags":[3224,3319,2601,3268,2976,2877],"byline":[914],"ad_cat":[],"legacy-category":[],"class_list":["post-2464384","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-exploration-survival","tag-core","tag-new-zealand","tag-science","tag-skin","tag-survival","tag-swimming","cluster-sweat-science","byline-alex-hutchinson"],"acf":[],"parsely":{"version":"1.1.0","meta":{"@context":"https:\/\/schema.org","@type":"NewsArticle","headline":"How to Survive 75 Hours Alone in the Ocean","url":"https:\/\/www.outsideonline.com\/outdoor-adventure\/exploration-survival\/how-survive-75-hours-alone-ocean\/","mainEntityOfPage":{"@type":"WebPage","@id":"https:\/\/www.outsideonline.com\/outdoor-adventure\/exploration-survival\/how-survive-75-hours-alone-ocean\/"},"thumbnailUrl":"https:\/\/cdn.outsideonline.com\/wp-content\/uploads\/2018\/01\/17\/survival-at-sea-sweat-science_h.jpg","image":{"@type":"ImageObject","url":"https:\/\/cdn.outsideonline.com\/wp-content\/uploads\/2018\/01\/17\/survival-at-sea-sweat-science_h.jpg"},"articleSection":"Exploration & Survival","author":[{"@type":"Person","name":"jversteegh"}],"creator":["jversteegh"],"publisher":{"@type":"Organization","name":"ºÚÁϳԹÏÍø Online","logo":"https:\/\/www.outsideonline.com\/wp-content\/uploads\/2021\/07\/favicon-194x194-1.png"},"keywords":["core","new zealand","science","skin","survival","swimming"],"dateCreated":"2018-01-17T00:00:00Z","datePublished":"2018-01-17T00:00:00Z","dateModified":"2022-05-12T18:42:20Z"},"rendered":"
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