That makes sense if the area around the pool is slippery. It's just that given the tremendous downside of risking the victim's life or brain damage, it seems that the paramedics wouldn't be risking much by hustling a little, rather than "walking slowly".

Unless it was really slippery, or if they thought someone was going to flip out to the point where it seriously interfered with the CPR, taking your time doesn't seem like the best thing to do for the victim.