17. Puerto Rico
It’s not exactly a pool, but it’s too crazy to leave off the list. Bioluminescent Bay in Puerto Rico is the kind of phenomenon that could freak out any first-time visitor: When they swim in the bay, a trail of blue light follows swimmers wherever they go. It’s not magic, but the abundance of single-cell organisms (as many as 720,000 per gallon of water) that give off this glowing color when they’re agitated.
I kayaked through here at night when I went to Puerto Rico. Easily one of the coolest experiences I’ve ever had.