The picture above is a burrowing anemone with the normal anemone tentacles and the mystery (to me at least) tube.
The channeled whelk above is hunting. At the right taperedend of the shell, you can see a razor clam just sticking out of the mud. That little clam was frantically trying to rebury itself and escape the predatory whelk snail.
A whelk egg case. Each little disk will hold several snail eggs.