Almost all fisherman are usually wearing raincoats coated with rubber and boots during fishing operations. It is said that when a man falls overboard, the loss of life would be due to the lack of buoyancy of his protective clothing, namely the rubber coated raincoat and boots. The purpose of the present investigation is to clarify the relation of cause and effect between the protective clothing and the accident of falling overboard. The following items were studied. (1) The investigation about the consciousness of fishermen of their protective clothing worn during fishing operations (2) The experimental testing of behaviours and condition of a man overboard wearing a raincoat and boots