Hazards
The greatest nightmare for the single-handed sailor is falling overboard. In fact, this may be the greatest danger for any ocean sailor, given the slim chance of recovering a crewmember lost overboard in the open ocean, particularly if the rest of the crew is asleep at the time (as will usually be the case for small crews). However, the nightmare scenario of floating in mid-ocean while watching one's boat sail away under auto-pilot makes many single-handers very cautious. Staying on the boat (by careful and thorough use of handholds, lifelines, and tethers) is undoubtedly the best approach for any sailor, but some single-handers tow a rope astern, as a last desperate chance if they should fall in.
There is some controversy about the legality of sailing single-handed over long distances. The International Maritime Organization navigation rules require that "Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision." Single-handed sailors can only keep a sporadic lookout, due to the need to sleep, tend to navigation, etc., raising the possibility of a collision with an unseen vessel.
Read more about this topic: Single-handed Sailors, Sailing Alone