a deep submersible light includes a body defining a hollow interior and a solid state light source such as a plurality of high brightness leds mounted in the interior of the body . a transparent window is mounted over the leds . the space between the transparent window and the leds is filled with an optically transparent fluid , gel , or grease , which allows light to pass through and ambient water pressure to pass in , thus pressure compensating the leds by allowing them to see ambient water pressure . the transparent window is mounted in the body for reciprocation in both a forward direction and a rearward direction to accommodate volumetric changes in the compensating fluid , gel , or grease caused by changes in temperature and water pressure as the manned or remotely piloted submarine travels from the sea surface to deep ocean depths .