New underwater boss and very difficult to make un-crafting table

So… using some items (idk what quite yet possibly a nether star on gender dragon egg or both) will teleport you to 10,000ish blocks away from land. In this place there will be a huge whirlpool in the center of the are that you pull you down under the water. I was thinking a giant megalodon or sea snake, something very scary with lots of heath, I was thinking it would give the blindness affect and look super terrifying. It could blow bubbles at you or poison you or strangle you, ( idk the details yet) but if/when you finally defeat it it will drop a “stone of the sea” (or a different name idk) this item, along with some other hard to get things will craft an un-crafting table, this will be super over powered, clearly, and it will be able to un-craft stuff (that’s kinda obvious) and yeah, that’s my idea.