They are about 2 meters tall, have long, mostly black hair, membranes between fingers and gills on the sides.
They have gills instead of lungs. The gills can extract oxygen both from water and from air.
As in deeper parts of the patian oceans oxygen is not a thing, they can also live without oxygen, but they are weaker then. Their eyes glow a bit, so they don't see any difference between light and dark place.
Lifespan of average patian is about one hundred thousand years.