Well, first of all, this is an awesome question.
As far as an answer goes, we have to consider the primary source of death and injury in a tornado. Very rarely is death from a tornado from being sucked up into the vortex and thrown thousands of feet. Usually death comes debris flying at extreme speeds coming into contact with a person or the collapse of a structure.
If the vortex were to go directly over the swimming pool, if the swimming pool were an above-ground deal, depending on the scale of the funnel (fujita scale), it would likely be destroyed by the force of winds given their broad surface area, in which case if you're in scuba gear you would not be in a good position. If it were an in-ground swimming pool, the water would likely be sucked up into the tornado, along with anything in it, unless it were an unusually deep swimming pool. Even if it were, however, and our hypothetical diver were at the very bottom, the turbulence of the water caused by the surface winds would likely kill or seriously injure the diver.
However, if the tornado were just passing nearby an in-ground pool with a depth of about 10 feet, I think the diver could survive.
Is this a good idea? Of course not! There are lots of better ways to find shelter from a tornado! Basements, underpasses, bathtubs with a mattress over them...
But I admit it would be pretty friggin' badass.
Posted 1424 day ago