The 360 degree light, which you have, is both a steaming light and an anchor light. One way on the nav light switch turns only it on, the other way, turns on the red and green and the all around white.
You have to remove the socket from the cabin house. You then route out both the screw holes, and the core around the light, and fill with thickened epoxy. Finally as you re-bed the anchor light, be sure that the wire is well embeded in a compound such as Boat Life "Life Seal"--a combination silicone/urethane compound. You want the wires to be flexiable enough to make the contacts, but also seal the hole. There is no reason if properly beded, that this will leak.