I worked on his design a bit more.
After studying the lives of aquatic mammals, I realized I will make Neptune with all other Lir's with thick fur that is double coated. This is for their body to keep their body heat inside while they go for their deep sea diving's for food and shelter from the Outer worlds. Though they are partially blind during the lighting of days, Their eyes can see excellent in the Night and darkness of the pits of the seas. The Salt water of the sea also helps them sea under the water as if it was crystal clear. Their large ears work like whiskers on a otters face, feeling the sea's vibrations to find the nearest source of food. Their tail's also help on the surface to create noises and vibrations for the Lir to outline the world so they could see, making them creatures who constantly are moving in some sort of way so they would not be blind like a bat.
Their mane is not only for good looks but as it rolls down the back it turns into a fur covered fin that helps break the surface of the waters and balance their bodies in the waters while swimming. The webs under their arms help navigate their bodies as well in the waters.

Lir species by Me