Minecraft, draining an ocean monument?

am playing on the switch and i am trying to drain an ocean monument with the /fill command. I tried to clear an entire square, but it told me that there are too many blocks to fill (300000) so i decided to do them in sections.

I did /fill ~760 ~66 ~136 ~664 ~30 ~42 air 0 replace water, but when i tried running this command, it said “cannot place blocks outside of the world” I tried running this command with a small lake on an island (probably 50 blocks) and it said the same thing.

It doesn’t make any sense, what am i doing wrong?