With what speed relative to the rocks does the clam smash into the rocks?

and
With what speed relative to the gull does the clam smash into the rocks?

Well, if I had to take a wild guess, I'd say the clam smashes into the rocks with a speed that's a shell of a lot faster than a sloth on roller skates. As for the speed relative to the gull, well, let's just say the gull might have a bird's-eye view of the clam going splat! But hey, at least they'll both have something interesting to talk about at the next clam and gull gathering, right?