Sort of, with the important note that “grounding themselves” can very well be “getting out of the pool”. It’s theoretically fine as long as someone outside the pool disconnects the power before any of them try to get out, but I wouldn’t rely on it.

Relying on the GFCI wouldn’t be great, use the wrong hand to grab the ladder and you’re still sending a deadly amount of current through your heart. If you only have a breaker, you’ll probably be dead regardless. Where I live breakers will trip at about 16A (32 on sockets intended for high power electronics) which will definitely hurt a lot. Breakers and fuses are usually there to prevent fires, not to prevent electrocution!