Aqualandia claims to be Europe's biggest water park, and it's huge. You can see it rising from the coastal plains long before you arrive, more than 20 enormous slides including the "Black Hole," a wet ride through the darkness, and the "Big Bang," the highest chute on the continent.
Younger swimmers can enjoy Adventureland, the best kiddie pool imaginable. There is also a wave pool, rapids, and plenty of playground equipment, restaurants, and shops on dry land. You could easily spend all day here, so don't forget your sunscreen.
Aqualandia Park is located just west of Benidorm proper; take Avenida Mediterráneo and follow the signs. Parking is expensive, but it's easy to get here by bus. From the center, Bus 11 and 47 leave hourly. It's better to buy your tickets at the station, then take buses 1 or 4, which free with your paid park admission.