Mangetsu
Steampunker
Not sure if this is a bug, or there is an updated version of Calamity somewhere, I don't know. But Aquatic Scourge does not spawn for me, whether naturally or with Seafood. I cannot get it to spawn at all. I've got the most recent version of Calamity on the Mod Browser, so I don't know what's up there.
...Have you tried spawning it in the sulphorous sea? (The sea on the dungeon side of the world, the one near the abyss)
I'll bet you have, but if you've tried it at a normal sea, it won't work. (Especially by judging the Seafood, which you need the sand to make.)