Shadow Caster Color Caster's
They have their own RGB controller. I'm not sure if you could have one control the other but that would be a Interesting question. The under water Light's have a pretty good draw as far as power go's. Most RGB controllers don't have they type of Horse Power to push an underwater light. So that would make me lean towards the Shadow Caster RGB controller controlling your boats interior RGB's Vs the Wet Sounds controlling everything.
Check with Ryan @ Chucktronics he has done lots of Crazy DMX controlled RGB's he's also a Shadow Caster dealer.