What mammal has a billswims like fish and is covered with fur?

Here's why:

* Billswims like fish: Platypuses have a duck-like bill that they use to swim and hunt underwater. This bill is very sensitive and helps them detect prey through electroreception.

* Covered with fur: Platypuses are covered in a thick, dense fur that helps them stay warm in the water.

Let me know if you have any more animal riddles!