you only need to pump it one time then its airtight unless water gets in anyway if you use o2 tank and ventillator its gonna do same thing no need for pumps (water displacement because of air from tank, water exits at entrances to base which then turn on forcefield (was off during "pumping") after getting air in base), maybe if ventillators only had specific power so you need more depending on depth. If you run out of o2 it doesnt flood because of forcefields, if you turn off power and open a door though... flood
So technically the ventilator will then also be a pump to pump in o2 and ensure its pressure is more the outside water pressure
I like what I have seen so far! As many varieties of atmospheres and creatures would be great for exploration. I think the size is just right!
For any real water base type setup, they need to add flowing water like they already have in Minecraft, Planet Explorers, 7 Days to Die, and others.
It would be really really cool if structures (of reasonable size of course) on planets would be visible from space, and even big CVs when landed. I wish for this because of the very small scale of the planets actually, and the relative big (possible) size of structures in comparison. If I can build a base as large as a lake that is visible from space, I would expect the base to be also visible. This could be simply a "snapshot" from above the structure added the the planet map. In fact I have no idea how it could / should / would / may / might be done, but the discrepancy between what is seen from space and what is actually on the planet is obvious with bigger structures. Of course if "real bigger planets" are in the plans and there is no "playfield loading gimmicks" between space and planet, than my suggestion is void. *hem*...