Watercoats are an original species created by Bliznets. They are closed; which means you can't get your own for free!
So, how can I get my own?
You can get your own by buying a MYO slot: that means you can Make Your Own for a few cents. You can also buy adoptables, or ask for a custom. The prices are here.
How can I know more about them?
This website is actually here to tell you everything about Watercoats! Their caracteristics, ways of life, and many other things.