I found these: http://www.alliedelec.com/search/productdetail.aspx?SKU=70099203 Some time ago.

I use one of them in the anchor well which is often underwater. With the watertight cover on they have been perfect. No metal housing to corrode, etc. I had a connector similar to the one you show up there previously and the metal corroded away in less that six months.

They are available in many configurations. I use a three pin for direct windlass control (normally I use a small radio control), and two pin ones for 12V deck outlets. They clamp a round wire so no need for sealants.

Defender used to sell these but dropped them.