This is what a hippocamp (or hippocampus) looks like:
The hippocamp is a magical horse breed that has the front quarters of a horse, and a fish-like back end. It is amphibious, and can be found on the beach and in water biomes. Even though it can move around on land, it swims better and can go quite fast in the water when it wants to.
Like any magical horse, you can tame a hippocamp and ride it! Unlike other magical horses, you can ride it just fine in the water, and even dive down into the depths of the ocean with it. And not only that, but if you're riding a tame one, he'll even keep you from drowning while underwater! Note that your air supply will drop down to half it's full amount, but it won't go lower than that (the hippocamp can't be expected to give you all his air!)
The hippocamp is able to breed with other magical horses, and can pass on his water breathing and fish tail traits. It is completely possible to get a magical horse that has a fish tail, horn, wings, flaming hooves, and large size (and even the cool ultimate unicorn hides). Hippocamps can also be named and given the skins and abilities of the custom unicorns you and others have made! Like this:
There are other new features in this update, like Spirit Trees and the Oracle.
So, what are you waiting for? Go get the update!