An assembly, in particular an underwater optical assembly is provided. The assembly comprises a tubular wall mount, a housing and a seal. The wall mount has a cylindrical bore portion and the housing comprises a head and a stem rearwardly protruding from the head along an axis. The head defines a chamber with a window for dry housing an optical device in the chamber and the stem comprising an enclosed channel in fluid communication with the chamber. The stem has a cylindrical stem portion mated to the bore portion. The assembly is configured such that in an assembled configuration the stem portion fits the bore portion in an axial direction, the head is located in front of at least the bore portion of the wall mount, the housing being attached to the wall mount and plugging the wall mount with the seal extending substantially radially between the stem portion and the bore portion sealing the assembly circumferentially watertight. The head has a radial head size and the stem has a radial stem size, wherein the head size is larger than the stem size. The head has one or more circumferential walls forwardly protruding from a substantially radial rear wall, the stem rearwardly protruding from the rear wall. The stem and the one or more circumferential walls each have a thickness in radial direction, defining a rear wall area between a radial outside of the stem and a radial inside of the one or more circumferential walls, wherein the rear wall has, for at least half the radial area a thickness in axial direction that is less than a thickness in radial direction of the circumferential wall, and preferably less than a thickness in radial direction of the stem.

A pool system includes an underwater lighting assembly installed below a water line of a swimming pool or spa. A method of installing the lighting system in the swimming pool or spa includes guiding a lighting assembly cable through a conduit outlet of a wall fitting, into conduit, and up to a location of a pool transformer. The method includes coupling a lighting assembly with the wall fitting. The lighting assembly is connected to the lighting assembly cable, and a portion of the lighting assembly extends into the conduit. Guiding the lighting assembly cable includes positioning a pre-wound section of the lighting assembly cable with a plurality of turns within the conduit.

A light fixture, methods for installing the light fixture, and systems that incorporate the light fixture are provided. The light fixture includes a housing that connects to a power source at one end and interfaces with a heat sink, lighting module, and associated lens at the other end. A lens retainer includes an aperture that allows water to flow into a cavity formed within the lens retainer when installed. A portion of the heat sink is exposed to the cavity and can form a surface of the cavity, thereby being exposed to water when the light fixture is submerged. The exposed portion of the heat sink can include a three-dimensional shape such as a V-groove to enhance heat transfer characteristics.