The ascent of a diver following sudden failure of his equipment is analyzed using basic physical concepts. It is shown that if he can begin his escape from the depths with a lung full of fresh air, he can expect to surface safely from depths in excess of 100 feet, even though the time of rise may be two minutes or longer. It is also shown that the most dangerous point of such an ascent is not as the surface is approached, but at a specified intermediate depth.