Paul has a list? Really? Hehehe! You guys never cease to amaze me.
lol, not quite. That's what we in the writing business like to refer to as "hyperbole."
I have, in the past, been able to spontaneously generate lists of options for random queries like this, but fish-related descriptions seem to be escaping me at the moment.
However... endearing and aquatic...
What about:
Flipper
Gill
Spongebob
the phrase "Wet behind the ears" comes to mind
Captain SCUBA
Moby D -- er, never mind
(Captain) Nemo
Reef Boy
Pool Boy
Water Boy
Lungfish
Aqualung
Flounder Face
Pain in the Bass
Kelp-for-brains
Sea Lion
Finhead
Any of those work for you?