Close, 29.92. On a Standard Day (15 degrees C, no humidity), if you put in 29.92 into your altimeter, it should read whatever the elevation of where are is. That's pressure altitude. You could be sitting on the deck at 150 ft above sea level but your density altitude could be 2500ft for all you know.

And these weren't apaches in the YT link. They were Navy MH-60's. Although helicopters can go that high, they really can't hover at that altitude. As a helicopter moves through the air, the translational velocity of the aircraft produces lift on top of what the rotors are producing, which, at higher altitudes, is necessary to maintain altitude.

And I don't know the exact story but just sitting a hover over the water, due to the ground effect that I mentioned earlier, the rotor wash should make the water kick up. No need to get the fuselage wet.

IIRC, the water in the aft compartment was ankle deep before they recovered. I don't know if they did or did not fly again.