"Cloyster is capable of swimming in the sea. It does so by swallowing water, then jetting it out toward the rear. This Pokémon shoots spikes from its shell using the same system."
If Shellder looked silly, Cloyster easily makes up for it, because it looks evil at times with that smile. That being said, Cloyster is one touch Pokemon, it's shell is hard because of the pressure of the seas that it lives in. In the anime, it took numerous pummelings from Ash's Kingler before finally cracking.
Cloysters Basic Attacks are Frost Breath, Tackle, and Ice Shard. While its Special Attacks are Icy Wind, Hydro Pump, and Blizzard.