sub placement

I have just installed 4 wetsounds xs-650 to replace my in boat speakers I want to place the sub where the freshwater sink is under the window? is this a good or bad idea? also what sub amp,amps should I use to power this? I am probably going to add the wet sounds threesome to the tower this spring? here are the photos of the sink location? any recommendations would be great
http://larsonboats.com/escape/204/