1the first pet most players ever get
Water Chests sit in plain sight on the ocean floor and the roll on this one is generous, so a swim on day two can hand you a companion before you have fought anything at all. If the chests come up empty, Ocean Crates and Seaside Crates cover the same ground once you take up fishing.
how it behaves
In water it swims around properly. Out of water it is stuck inside a bubble bobbing along behind you, which is the better half of the gag. It picks up speed when you outrun it, so it never gets left behind on a long trip.
two references at once
The pet is the Baby Shark song, down to the shape of the sprite. The name is from Finding Nemo, where the tank fish saddle Nemo with it as a nickname, which is also why the bait in the icon is a clownfish rather than anything a shark would actually chase.