I would hope no one would try to swim in one, but if you empty the pools where the vast majority of America's nuclear waste is stored, most people would say the resulting cavity strongly resembles a swimming pool.
You can swim in spent nuclear fuel pools. I know a professional diver who did it for a living.
Love the revelation that swimming down to touch the spent fuel rods would be fatal. Pro-nuclear folks don't like facts like that because they want to pretend that either there is no waste, the waste won't hurt you, or we've solved the problem of storing it safely. None of these is true.
Nuclear professionals are made acutely aware of the dose they would get on a work task, and what to do if the conditions aren't as expected. This kind of work isn't a "do whatever you feel like" scenario.