Cloyster  are bivalve Pokémon, guarded by an extremely strong, multi-layered shell. The shell is strong enough to withstand a bomb explosion and cannot be pried open by even those with superior strength. Nobody has seen their dark innards, which are Cloyster's weak spot as they are very soft and vulnerable. They launch thick, powerful spikes at enemies in battle, as well as to capture prey. These spikes are even stronger than their shell. Cloyster can also crush prey by clamping their thick shell shut onto them. When being attacked, they simply shut their shells to avoid further damage. To travel through water, they swim by swallowing water and jetting it out opposite to the direction they want to move. Evolves from Shelder with the use of a Water Stone.