Just outside the Marine Bay Sands Shopping Centre in Singapore the Whirlpool swirls that water down to the lower level pool where the Sampans sail. Quite a few people were rolling coins down with the aim to get the coin into the central hole. The Whirlpool is actually a whispering wall too as when you lean a bit closer to the rail you can here people talking from over the other side. True! Try it when you visit there!