[help] Clipping one mesh out of another?

Hello everyone!

I'm having a bit of a boggle. I have a [boat set up,](https://i.imgur.com/88LezZX.gifv) but I want to make it so the seawater doesn't render inside the boat. The best solution I can think of is a location based opacity mask, but I'm unsure how to apply this to a mesh rather than a sphere or square volume.

What direction should I be looking in for this? Is there a better solution?

Thanks!