The crossword solution for the term 'Go Up and Down in the Water' is BOB, which stands for buoyancy-operated bathysphere. A buoyancy-operated bathysphere is a deep-sea diving device that is used to explore the depths of the ocean. It is designed to move up and down in the water by controlling its buoyancy. The bathysphere is made of a steel sphere with a hatch on top, and it is filled with air or other gases to control its buoyancy. It is connected to a cable that is used to lower and raise the bathysphere from the surface.