This is Montegrotto Terme, Italy's recently completed 'Y-40' (aka 'The Deep Joy', which I've actually been called before), the new world's deepest swimming pool (previously: this one). The pool's central well reaches a depth of 40-meters (~131-feet) and is used for deep-sea diving practice. The pool also features several underwater viewing areas (including a clear tunnel) and is filled with spa water kept at 32 - 34°C (~90°F). That's nice and toasty. Still, 131-feet deep? How high is the high dive, a mile? Because I jumped off the highest Olympic diving platform once and I'm pretty sure I got brain damage. My mom said it was just swimmer's ear, but she keeps a lot of things from me.
Keep going for a video of the pool, including a guy heading to the bottom.
Thanks to Bryon, who once rested his head on the bottom of a 20-foot pool and was convinced it was going to explode.