When Captain Jessica Tyson boarded a ship in her years at sea, she usually took a piece of rope to use as a belt.

It is a strategy that she said women at sea often use to make a boiler suit designed for a man’s body fit them better.

“Women are different shapes,” said Tyson, a former tanker and cruiseship master who now works as a port pilot and marine surveyor, as well as serving on the advisory board of the charity Human Rights...