I can't draw fins :( - she was left alone by her family because she didn't wanna be aggressive [betta fish are known to be alone, they don't get along with other fish] towards other merfolk [she was really young] so of course nico's family which were s h a r k s took her in - she helps nico on his ship as a second-in-command since he gets drunk sometimes so Cass just, steps in and doesn't let anyone see him when he's not in the right state :D - doesn't really go into the deep waters that often [since more dangerous merfolk are there] so she always goes with nico despite him being hurt there before