Coreel is a dual type Water/Rock Pokémon.
This prehistoric Pokémon probably inhabited tropical seas, living in coral reefs, so the colors of its skin and the seaweed-looking crest had mimetic purposes. Due to its small but sharp teeth it’s supposed that its diet included small fishes and coral itself, allowing this creature to grow a protective rock armour on the ventral part of its body.
Its wide eyes allowed it to see clearly even in deep, dark waters and in underwater caves where it probably used to hide from bigger predators. The gills allowed it to wait, hidden, for long periods.
It is resurrected from a Fin Fossil and evolves into Lochreef starting at level 40.