Seahorses

Seahorses... these graceful, appealing ocean creatures have nasty personalities. They enjoy shooting foes at range, which they do very effectively. They are also rather strong, flexible, even intelligent, and they take a fair amount of punishment to be defeated. This makes them dangerous foes.

As the name says, they are found at sea.

One of the few friendly seahorses seen in the Ultima games is Blissfull in Ultima IV.