Repost because I totally screwed up the Subject last time :/

How do I get into underwater Collasium?

1 building with nothing in it

1 building with a broken door that I can't get into

1 building with a switch to load the next area. I get inside and find a squid door that won't open.

I've tried everything I can think of, but still can't get in. Killed the hydra and everything around cet's pyramid also, but didn't see any
hints there.

Baff

The building with the broken door, go down and look at the right side of the base of the building there is an opening there...