GENEVA – The disappearance of many sailors has been blamed on something that doesn't quite seem real: hallucinations, which have even prompted sailors to believe they had reached port and to climb over the railing of their boat.

Loss of lucidity, loss of bearings – sleep deprivation can wreak havoc on a sailor’s mind, to the point where it creates a state very similar to a hallucinatory drug trip.

French skipper Jean Le Cam smiles when asked about hallucinations: "Sometimes you’re just too tired. On solo round-the-world races like the Vendée Globe, if you get to the point where you’re that tired, it can have serious – dangerous – consequences," he explains. "During the 2004 race, we all pushed our limits to the max. I was so tired, I couldn’t sleep anymore."

At one point Le Cam thought he saw his sister on the deck. "I held her in my arms but when I woke up, I was just hugging a sail. It gets surreal. When you start believing that people are on the boat with you, you know you’re starting to go nuts. That’s when you try to sleep, if you can," he says. "Often it’s difficult to find the right time for a nap, but you really have to find moments to rest, otherwise things will start to go in a tailspin. Since the beginning of this race, we haven’t been sleeping much. For me it’s about four hours a day max."

Speaking on his satellite phone, Swiss sailor Bernard Stamm recalls his nicest hallucination: "On this Vendée Globe, I haven’t had any yet. When you do hallucinate, it’s because you’re having serious sleep deprivation. During the Around Alone solo around-the-world race with stopovers, I was freaked out by one of my waterproof jackets. I thought someone had gotten on board. In the long time it took my brain to realize what was happening, I had time to flip out. Then I realized it was my oilskin and not someone who was after my cute little body."

French sailor Michel Desjoyaux, who won the race twice, recalls that fellow French skipper Roland Jourdain once thought his compass was the bloody head of a monkey who was trying to eat him: "Instead of little white bars between the cardinal points, he saw teeth. According to him, there also was a cow on the boat," says Desjoyaux.

Visions of animals seem to be quite common. Swiss skipper Dominique Wavre had a feline encounter: "My boat had a complete electric breakdown and so I was using small green lamps to light the compass. It looked like cat’s eyes in the night. I could feel it brushing up against my legs, trying to get some food out of me. In the morning, I found my sandwich in tiny little pieces at the bottom of the cockpit – because I had fed him. Once I also found myself in a field, surrounded by cattle," confesses the Geneva skipper.

"Something that happens very often is when you see a mate at the bow of the boat, and you scream at him for not being at the right place, when in fact, it’s actually just a sail."

Another thing that happens often is when you hand over the steering of the boat to another sailor to go get some sleep. It happened to Michel Desjoyaux: "I was 4 days in the Solitaire du Figaro solo race. I found myself in the company of French skipper Vincent Riou who, in fact, was on another boat. I remember saying to him: "Vincent, take the watch, I’m going to bed, wake me up when the wind picks up." So I went to sleep and when I woke up after a couple of hours, I really kicked myself."

When seas hallucinations turn deadly

He says, "a hallucination isn’t a physical affliction, it’s all in your head. It’s like a dream except you’re fully awake and fully stupid. In most cases it’s not too bad, you just need to catch up on sleep and after that, everything starts making sense again and your reflexes kick back. What’s dangerous is when you start wanting to disembark because you think your boat is at dock. I remember a competitor in the Solitaire du Figaro who had called his competitors on his VHF radio to say ‘What the heck – my boat has no fenders, I can’t dock.’ We were in high seas."

Legend has it that this sailor – who shall not be named – actually did step off his boat once, but fortunately he was wearing a harness. This anecdote impressed Damien Davenne, a chrono-biologist and sleep specialist at Caen’s STAPS University: "I’ve heard similar stories from a couple of other sailors. Some of them told me they were dreaming of arriving at port, with the crowd cheering around them and so they stepped off the boat. When they are hallucinating, they can’t tell what’s real and what’s not. It is believed that sailors have been lost at sea after stepping off the boat during a hallucination."

When sailors describe their hallucinations, says Davenne, it’s reminiscent of descriptions of LSD trips.

There’s a fine line between daydreaming and paradoxical sleep. "It’s easy to wake up from a dream when the alarm clock rings in the morning but when you’re trying really hard not to fall asleep, dreams can be quite intrusive. This is what hallucinations are," he explains. "It’s when someone who is sleep deprived has a day dream that turns into a reality. There is a thin line between reality and illusion – but it’s there when you have enough sleep. But if you’re sleep deprived, the dream – which is essential to life – starts invading everything, paradoxical sleep and deep sleep."

This is why Swiss skipper Yvan Ravussin, during the Jacques Vabre trans-Atlantic race, couldn’t wake his brother up. "He was dreaming that we had capsized and someone was knocking on the boat’s overturned hull."

Damien Davenne says getting enough sleep is vitally important. "It’s a biological process called circadian rhythm – our internal clock. The human being must spend 1/3 to 1/4 of his time recuperating. If there is not enough recuperation time, the system crashes. During sleep, the brain filters the good from the bad and only keeps what’s necessary for survival. Sleep deprivation intoxicates the brain and this intoxication forces the metabolism to stop at some point."

"What we admire in sailors is not their ability to go without sleep, it’s their ability to recuperate when they need to." For these reasons, solo sailors need to know themselves really well. Davenne insists on the fact that "genetics determine what our needs are. They differ from one person to another. There is no survival without sleep and when it is well managed, sleeping is absolutely not an obstacle to victory, on the contrary. In a Vendée Globe, those who end up winning are those who know how to handle their recuperation periods. Michel Desjoyaux concurs, the more he sleeps, the easier it gets."