Pacific Spiny Lumpsucker - Eumicrotremus orbis
Some people describe the Pacific Spiny Lumpsucker, Eumicrotremus orbis (Scorpaeniformes - Cyclopteridae), as a ping-pong ball with fins, and yes it seems to be that.
Usually located in eel grass beds at night, these comical fish have a modified pelvic fin that works as a suction disk. This disk is used to attach the fish to rocks, shells and blades of eel grass. When disturbed, the fish hovers about, changing directions aimlessly like a tiny helicopter (they are very inefficient swimmers).
They are quite common, ranging from the waters off the Washington coast, up around the arc of the Aleutian Islands, to the Asian mainland and the northern islands of Japan, and in the Bering Sea.
The largest recorded Lumpsucker was five inches in length, but the most of the lumpies that divers see are about the size of a quarter.