water room
/ˈwɔːtə ruːm/ /ˈwɔːtə rʊm/noun
1Space for a fish, ship, etc., to move about freely in the water.
2Any of various kinds of room in which water is stored, used, etc.
Origin
Mid 17th century; earliest use found in Izaak Walton (1593–1683), author and biographer. From water + room.