Probably OK - some of the better hard drives can take a beating, I would stay away from a 7200RPM or faster but should be fine with a notebook drive at 4200rpm or a 5400rpm regular drive...
Could even use a 1GB microdrive which is even more shock resistant but that's probably a little too slow..
You fish at 30 knots? Wow - no wonder you won't catch 'em

- you don't need to work detail at 30 knots, but when drifting of working a particular ledge - it'll come in just fine...
So what CC are you getting, did you get?