It was a joke, that by making people drown less with salt in pools, one'll get other deaths.

And all the effects salt has on our environment and us. One big point is that non-saltwater organics will die at even low concentration of salt in f.e. in soil, while saltwater organics will die too when salt concentrations level "dead sea" will be spilled into canalization system/rivers wherever.

Of course it's not deadly to swim in salt water. But the salt water is deadly by itself.