Not seaworthy is a term used to describe a vessel that is not fit for sailing due to structural damage or other issues. The term can also be used to describe a boat that is not safe to sail in rough waters. The crossword solution LEAKY is a five-letter word that describes a vessel that is not seaworthy, as it has a hole or crack in its hull that allows water to enter the boat. This can cause the boat to take on water and sink, making it unsafe to sail.