I've read that nuclear waste is stored in Olympic-sized swimming pools, but what is it about water that so effectively stops radiation? And apparently, this shielding effect of water is so powerful that one could literally stand right next to the pool (and according to some things I've read, they could even accidentally fall in) without suffering any ill effects whatsoever. But why? Water, chemically is h2o of course, but what is it about this compound that would be able to block such powerful rays that are capable of traveling through solid objects? Because X-rays (which are also emitted by nuclear waste if I'm not mistaken) are capable of traveling through the body and even through cargo in airports. These objects are solid, yet water is a liquid and stops them. Also, why is it that visible light is able to extend through water, but not the higher spectrum stuff (e.g. x rays and gamma rays)? Because one can see the waste at the bottom of the pool clearly, yet the radiation cannot reach the top of the pool in any substantial quantities? Also, I'm aware that ozone (in trace amounts in the upper atomsphere) blocks a large amount of high frequency radiation (UV light) despite being present in the thin levels of the stratosphere. What is it about ozone that has protective qualities? And in general, what determines if a chemical is likely to block high frequency radiation or if it is likely to pass through it?