Of Lakes & Mountains (can you answer this riddle?)

Huh? Well What if we have two lakes. One is located here in Michigan and I go under about say, 10 feet. The second is on 10,000 ft. elevation. If I dive into the 2nd one at the same depth, how will the pressure compare to the 1st? Interestingly enough, if we try to compare air pressure then we will get it suspriciously close. Why? The air pressure is calibrated depending on elevation, so normal pressure at sea level=normal pressure at high elevation, because they're indicator is set up that way. It's not really equal. How about water though? Shouldn't we be crushed? I mean doesn't air have a much lower pressure and density!? I've read recently that it's actually the air that has a higher density; WTF?! Then why can't we swim in it!? Why do people troll like that and get passed off as experts? I'm, well, pissed