This is the swimming pool art installation in 21st Century Museum of Art, at Kanazawa, Japan by artist Leandro Erlich. The top surface is filled with 4 to 5 inches of water that looks like a realistic pool. The people underneath the swimming pool can actually look above with realistic water effect on top of it.
A layer of water only some 10 centimeters deep is suspended over transparent glass. Below the glass is an empty space with aquamarine walls that viewers can enter.
The Swimming Pool has the size of 280x402x697cm (HxWxD), and the separating layers were made using two clear acrylic glasses about a foot apart and the space in between are filled with water.