Why don't you just drain Capricorn a-net
and where are the sharks going to live? unless they become land sharks.
Everywhere there was water just turn it into sand, the sharks can mutate into skelks. :-)
They’re just kittened
As others have stated before in some other topics : the issue is the very existence of that single map requiring three extra pieces of equipment + sigils and a second skill set. It would have added a bunch of extra work in making the new build UI.
That is why they are removing it for now, they will probably put it back when they have the time to put the underwater weapons in the new UI. Maybe they won’t even bother with the underwater weapons and they will indeed drain it, who’s to say? Meanwhile, this is their reason for removing it.