This nudibranch has long finger-like protrusions on its body. It is less than a few inches long.
I believe this crab is called a porcelain crab. It is less than 2 inches across and lives in anemones.
This little crab, less than 1 inch across, helps provide perspective on the size of many of the creatures in this album. This crab is standing on the side of a much larger anemone.