Abstract: An underwater light assembly for internal illumination of swimming pools and the like which operates on batteries and does not require any externally-provided current. A partitioned compartment is detachably engaged within and against a transparent dome. The compartment houses weights to keep the assembly submerged in a pool of water. The compartment also houses the batteries and a power assembly for providing current to a lamp socket. The lamp socket is suspended within the compartment. A detachable seal is provided to seal the compartment within and against the transparent dome. A metal contact plate is provided on the detachable seal such that, when the seal is inserted and seals the compartment within and against the transparent dome, an electrical connection is completed and the power assembly supplies current to the lamp socket.