The Beast Fears Fire - Hippothalassoi

Hippothalassoi [Violence 4]
Impulse - To Wreck Your Ship

Hippothalassoi are exactly what you might expect.

There's not a lot that's mysterious about 10000 kg littoral-dwelling behemoths, really, other than how they got to be in the coastal areas of the Bogsong. The local story is that one of the Dukes of Crickton tried to have them imported as a curiosity for a zoological garden and the ship wrecked near the Bogsong. Research doesn't bear that one out, exactly - the Duke and the Murren royal family in exile don't have that kind of money and pretty much live as guests of the Republic. There's also the fact that the zoological garden capable of containing even a mating pair of hippothalassoi would, by necessity, not allow anyone to view them. The most plausible explanation is that a pod of them got caught up in a storm and followed the ocean currents to the Bogsong. Whatever the case, these giant, bad tempered herbivores found the place to their liking and took over pretty extensive stretches of the Bogsong Coast.

Harm 4 There is nothing mysterious about these creatures and what they will do to you if you are handy. Hippothalassoi take the aggressive bad temper of their hippopotamus cousins, double the mass and add a healthy supply of mean. Far beyond territorial, hippothalassoi seem to enjoy destroying things that happen by. They are slightly more omnivorous than their river dwelling cousins, too, though predation by Hippothalassoi is pretty rare. They absolutely kill you if they happen to notice you, but they generally won't eat you. Comforting, I know. Hippothalassoi are infamous for being mortally offended by the very concept of boats; bulls will gladly violate the territory of other pods, even swim out into deep waters to attack a boat or ship he sees.

That Sinking Feeling
If you are on a boat or ship that a hippothalassos decides it doesn't like, make peace with your gods and and face Violence
On a Hit, you keep the animal at bay for long enough that whoever is piloting your conveyance can attempt to make an escape.
On a Hard Hit, you can also do harm to it.
On a Miss, the good side, is you might be able to see your house from the heights you reach before you hit the water and suffer Harm as stated.

There's Nothing Unexpected about the Water Giving out
Hippothallasos tusks occasioanlly get harvested for ivory, but hunting the beasts is, as you might imagine, all kinds of tricky. Some people have made outer-clothes from hippothallasos leather, or boiled it for armor, but their skins aren't really much different from cowhide.