Boni: It is kind of a spa.
I've been in the thalassotherapy pool on the Celebrity Infinity. It is as big as a swimming pool, but is something else! Like warm mineral waters. The pool on the Infinity had stainless steel loungers underwater along the sides of the pool in addition to big shower pipes above the surface you could stand under for a great waterfall effect. We were on an Alaska cruise and we would come back to the ship everyday and jump in the thalassotherapy pool to warm up. It was awesome!