Well let me start by wishing you the very best in luck at actually seeing several & hopefully close up if that's the only lens you'll have. From the sound of it you're not sure about using Tv but that's OK because it can do the job, but you may need to try a few different shutter speeds to hit the best setting for the lighting & conditions (stability of the boat). I shoot a lot of action, and have used a 7D for that purpose plus I'm a diver so I've been on many a boat while plowing through waves so here's my recommendations. Set the AF to AI SERVO, set the drive to shoot in "spray & prey" mode (at least 5 FPS) & shoot short bursts when appropriate.
TEST your settings while on the way to the the observing area, and check what aperture the camera uses with your Tv setting. If it's between f 6 & f 11 & the exposures look decent you're close enough to try it in action. (use Exposure Compensation as needed for MINOR adjustments but if they need a major change use different settings (shutter speed) . The key to success will be to use a shutter speed AND ISO that keeps you in the F 6 to F 11 range BUT doesn't force you to use slower shutter speeds while on a moving boat. Water like snow can trick the light meteringso check the LCD & adjust as necessary but higher shutter speeds are better than lower ones thanks to the fact everything will be moving including you.
WARNING. your camera & lens DO NOT like salt water or spray, so be very careful in choosing when to get it up to shoot.
"A skill is developed through constant practice with a passion to improve, not bought."
