Never by accident but several times on purpose- 5 feet of water and 10 feet from shore in a spot I know very well. Tanks needed vis any way and IMO it's good to know exactly how your reg actually responds to very low air pressures. I can tell you that anyone who says they are going along wtih no signs of any problems and suddenly the reg stops working because they are OOA is full of BS. Once your tank drops below the regs IP pressure- 140ish for most regs, the reg gets more and more difficult to breath from with each breath but it's over a span of several minutes, not instantly and the last dozen or so breaths are like sucking mud through a straw, you get air but you have to work for it. It's an experience you should try in a VERY controlled setting, it is nothing at all like the OOA demo where your gas is cut off at the tank. There is no excuse for being OOA (short of major equipment failure) to start with but you have to totally ignore what your equipment is telling you to end up in a real OOA.