Via Beginner’s Blog Otter
Thanks, Amorpheum!
Via Cloudtail
Via Das Otterhaus
Via Reddit user isisis, who writes:

A few years ago, I was having one of the worst days of my life and decided to chill at the Seattle Aquarium. I watched an otter fall asleep sucking his tail. It made my day so much better.

Submitted by chetchez!
Thanks, steamdragon!
Thanks, hepkitten!
Thanks, steamdragon!
Via Ed Bierman