An underwater light having a sealed polymer housing includes a rear housing component formed at least in part from a thermally conductive and electrically insulative material, an electronic assembly having at least one light-emitting element mounted thereto, the electronic assembly in thermal communication with the rear housing component, and a lens mounted to the rear housing component and forming a watertight seal therebetween, the lens and the rear housing component enclosing the electronic assembly. At least a portion of the rear housing component conducts heat away from the electronic assembly to cool the electronic assembly.