There is a 15ft x 8.5ft x 1.5ft area on my terrace which I want to convert into a small pool which will act as a splash pool for my kids and a chilling area for my in summers, which last for around 8-9 months in this part of the world. The area is already tiled but since its terrace I don't wist to take any chances and hence I want to get it waterproofed. The area will be covered in order to maintain cleanliness and unless required we shall drain out the water after usage.
What is the simplest form of waterproofing ? What else do I need to take care about ?