I would want a stock. A couple slugs to the waterline of a fiberglass hulled boat chasing you could make their day very bad indeed.
For boarders I have been becoming a fan of these.
My HD shottie is loaded with 00 buck (2 rds) followed by these (2 rds) etc.
It takes just short of all day long to sink a boat of any size with a .75” hole, LOLz. Even the bilge drain plug is bigger than that!
And if it has even the weakest electric bilge pump ever made, it won’t sink at all.
Boats are a LOT harder to sink intentionally than you’d think. It’s actually far easier to sink them by accident. That’s been my experience, at least.
I hope your insurance company doesn't see your statement. 
