There are two more waterparks in Madrid but
Aquopolis is said to be the best of all.
None of them open until mid June but here it is the information anyway.
AQUAMADRID
Ctra. de Barcelona N-II km. 15,500
Tel: 91 673 10 13
San Fernando de Henares
Buses: Continental-Auto from Parque de las Avenidas / Puente de
la CEA / Canillejas. San Fernando bus L-1.
AQUASUR
Antigua Ctra. de Andalucía, km. 44 (Aranjuez)
Tel: 91 891 60 34 / 91 891 25 75
By the way, public swimming pools will open this weekend in Madrid. I'll try to compile a list of all of them and put it in my website.
Summer is coming...