The children's game of Marco Polo is played in a swimming pool. The game is common to many different regions of the world.

The child who is "It" must swim around the pool with their eyes closed, attempting to tag the other players. The "It" child can only sense where the other players are by calling out "Marco!", at which point all the other players are required to yell "Polo!". By judging where the sounds are coming from, the child who is It is able to overcome their self-imposed blindness and hopefully tag somebody else, who then becomes It.

There are other rules to this game, varying from region to region, such as fish out of water. In this variant, as the It child swims around attempting to tag the other children, they may yell "fish out of water". If at that time there is someone out of the pool then they become "It". The person who is the "fish out of water" must be entirely out of the water, with no appendages in contact with the pool water.

There is a similar game, called Blind Man's Bluff, that take place on dry ground, out of water.