Just like how drinking seawater gives you the bottle back, using toxic sea water in jewelcrafting or brewing should give you the bottles back.
Reasoning
Bottles are very inconsistent to get, since they’re mostly from chests. There’s no NPC that sells them in bulk, so when using groups of 5 or 10 toxic seawater at the same time and getting no bottles back is very aggravating.
having an infinite source of toxic seawater with no cost for using it whatsoever is kinda op. all it takes is going to the dark sea for a minute and you got hundreds for free whenever you run out