The world's deepest swimming pool will open in Poland later this year, complete with underwater caves and overhangs. As a training spot for professional scuba divers, it can go as deep as 45 meters. Deepspot pool will hold 8,000 cubic meters of water, the equivalent of 27 Olympic-size swimming pools. About 1,100 tons of steel are being used to reinforce its structure, which includes a simulated "blue hole" plunging to its deepest point. (Photos: VCG)