Now the deepest one can be found in Italy. The place name is Y40 and it´s in Montegrotto Terme. The place was opened in 5th of June 2014. Surface area is 21 x 18m and depth is 40m / 131ft. Water temperature is 32 - 34C, so it´s possible swim and dive there just using normal swimming costume.
Watch this video to get better idea of the place.
Regards,
Mika