Lost Paradise is a water park in Bahrain. It is out of town a bit but is worth the drive. It is 10 minutes from the Causeway 20 minutes from Manama. It is an outdoor water park but even in 115 degree weather was very enjoyable. It is not a huge water park but there is enough to do to keep you busy all day. The crowds were non existent when we were there. We went on a Friday. (Their Sunday so that may have helped.) We never had to wait in a line and were able to do every slide at the park. It is a very nice park and we look forward to going back.
Wave Pool Beach
Lazy River Water Dump
This is how you know this isn't in the U.S. other than that it could be.