Cptn Latanica

If you don't mind farming 300 Red Essences per fight, sure it's okay money.

You don't have to get 300 Red Essences to refight Capt Lat. The "Return of Capt Latanica" quest (rewards 1 White Essence) requires killing 100 Slimy, 100 Jr. Selkie and 100 Mr. Anchor. It's an insanely easy quest.

You're thinking of the quest "The Lost White Essence." You can't do that quest once you defeat Capt Lat, and it'd be dumb to keep doing that one over for a White Essence, anyway.