Abstract The availability of immersion suits on board merchant ships is recommended in 1983 Amendments to the international convention for the safety of life at sea, 1974 (IMO). Suits approved by the Federal German Republic were tested in a wave tank using an immersible dummy. Extra buoyancy in the head region was required to correct the horizontal floating position. Buoyancy from a life-jacket was preferred to other sources. At 1 m wave height, flooding time of the face varied from 0.3% for one suit to 100% for another. Suits lined with non-absorbent material gave the best results.