There is no word about the Deep Workers having the ability to pump water back out at depth, but surely they can? If one is willing to forgo the ability to make buoyancy adjustments at depth, it gets really simple. Mark Ragan and Greg Cottrell both use tanks inside their subs with no way to be pump them out at depth. In Mark's case, it's just a soft plastic bladder that he uses as a pillow to get more comfortable!Alec