It's duck hunting in the sea, and it does give you access to some ducks that you won't get hunting near land. I think scoters and eiders are examples of ducks that you can only really get somewhat out in sea (you might be able to get them in a bay). It's in the middle of the water without much of a blind for cover...it's a very odd way of hunting.
ETA: Wiki "seaducks" for a list of ducks. Not all of them are 'exclusive' to the sea though...for example you can get mergansers and goldeneyes near land.
This post was edited on 1/20 at 6:22 pm