A watertender is a crewman aboard a steam-powered ship who is responsible for tending to the fires and boilers in the ship's engine room. Alternative terms include fireman and stoker.
In the United States Navy, "watertender" (abbreviated WT) was a petty officer rating which existed from 1884 to 1948. Watertenders held a paygrade equivalent to today's petty officer first class. A chief watertender (CWT) paygrade was established in 1903. In 1921, the lower paygrade was split into watertender first class (WT1 or WT1c) and watertender second class (WT2 or WT2c). Another lower paygrade, watertender third class (WT3 or WT3c), was established in 1943. The watertender and boilermaker ratings were merged into a new "boilerman" rating in 1948, which merged into "machinist's mate" in 1996.
WT also stood for Weapons Technician, a rate established in 1986 from enlisted who were Gunners Mate Technicians. The Gunners Mate Technicians were created from the NW (Nuclear Weaponsman) rating in 1962 and the NW rating was established in 1958. The Weapons Technician rating was disestablished in 1995 concurrent with the removal of tactical nuclear weapons from the fleet.