Ness Creatures

The Ness Creatures were the bane of all seamen. Found in lakes and oceans, it was a serious threat to shipping whenever it is encountered. The existence of these creatures was eventually verified when one sank the frigate Pembroke in full view of an armada. With the destruction of Exodus, the Ness Creatures were destroyed as well, ending their threat.

They were found, as said, in the ocean.

The Ness Creatures only appeared in the Age of Darkness trilogy, from Ultima I to Ultima III. In all three installments, mostly due to technical limitations, they didn't change at all.

Lore
''The seas surrounding Sosaria are home to a number of beasts, among which numbers the dread Ness Creature. For many years these reptilian behemoths were thought to be naught but the workings of the overwrought imaginations of mariners. The sinking of the frigate Pembroke in plain view of a small armada hath disproven this belief.''

- from "The First Age of Darkness", Ultima I

If it weren't so big, it might be a swan - until it comes after your frigate.

- from "The Second Age of Darkness", Ultima II

''Small cousins of the Great Earth Snake, these creatures can destroy an entire ship. In conflict mode, they can hurl magic across water, making it hard to fight them.''

- from "The Book of Play", Ultima III