I really think that is unlikely, most likely it is far below the surface, neutrally buoyant, or it sunk like an anchor. Trapped inside? No doubt.i think the point of the sealed hatch only being able to be opened from the outside is that even if they surface there isn't any escape. it could i guess float up on some distant shore someday but the folks inside will be trapped inside.
Any Navy Submariners on OK Shooters? Really curious to see what they have to say. Navy Submariners have been under the ocean at great depth and perhaps in the proximity of a nuclear reactor using U-235 as fuel, while worrying about russian subs, if that's not under pressure I do not know what is!