а говорят земля не плоская

Nice. I didn't find a way to skip a map trigger, but I did find a way to activate an event trigger early.
It's where you find the singularity bomb.

The game expects you to take the bomb and then use a newly-formed passage up to the walkway.
Well, there is a metal platform floating right next to where that passage would be. If you can shove it out of the way, you have a way up early, activating the rising water trigger without taking the bomb.
I never went farther because I didn't want to break something and have to start all over, but if you want to try it out it's there.