Why doesn't water enter a submarine from below when a hatch like this is opened under water?

>the pressure of the air is equal to the pressure of water at it's interface.
Not in a submarine.

Loooooooooool

Are you memeing? If the bottom hatch is open, and water is not flowing in, then yeah, it has to be equal.

rofl

So you're assuming water isn't flowing in to prove that air won't flow in?

>If the bottom hatch is open, and water is not flowing in, then yeah, it has to be equal.
I may have misunderstood what you were trying to say.

Obviously yes, once the pressure inside the sub is the same as outside, water will stop flowing in. However, initially (at the moment the hatch opens) the pressure inside will be much lower than outside, and a significant amount of water will need to flow in before it equalises.