Clamperl, the Bivalve Pokémon. Clamperl holds a powerful shell that’s useful in not only protecting itself, but also in clamping down on prey.
– May’s Pokedex
Clamperl looks like a baby Pokemon, because it looks like a baby pearl sleeping in a shell. It can evolve into Huntail or Gorebyss, depending on the held item when traded. Even though Clamperl is a clam, it somehow evolves into fish Pokemon.
Stat-wise, Clamperl has good Defense and decent Sp Attack, but low Speed and HP. It’s the only Pokemon aside from Shellder to learn Clamp. It also learns Shell Smash in Gen V, one of the best stat-boosting moves in the game. Clamperl feels a bit like filler Pokemon to me, though I do remember seeing a video on Youtube of a Clamperl sweeping legendaries by using Rain-boosted Surf, while holding a DeepSeaTooth (which doubles its Sp Attack), while Trick Room is in effect.