The Sailcloth Shroud (1959) by Charles Williams

A novel about a sea captain trying to clear his name of three deaths that took place aboard his boat. Williams, a former merchant marine, is perhaps best known for 'Dead Calm' and 'The Hot Spot', both made into films. Williams was the author of many nautical mysteries. Basis for the 1975 film 'The Man Who Would Not Die', co-scripted by mystery writer Charles Chesbro and featuring Dorothy Malone, Keenan Wynn, and Aldo Ray.