There are companies that rent out isolation platforms for helicopter filming - I'm pretty sure one of these would work.
There's a caveat... getting really sharp images requires world class accelerometers, closed loop control and careful balancing. This is expensive. We've built such a machine at work that's good enough to mount a telescope on and fly it in very turbulent air ... but there are 6 zeroes in the price tag and the first digit is not 1.
On an amateur budget, I think it maybe quite feasible if you can construct a gimballed mount to isolate you from the boat's motion. Provided the boat's not accelerating (apart from vertically,) you can deal with pitch, roll and yaw by suspending a large "+" shaped mass on a stiff rod under the camera's CoG and allowing it to swing. Light damping - as close to critical as you can get - would be a good idea.
Phew!...That's a fair amount of trouble and expense just to get some night sky shots.