Marco Polo is a form of tag which is played in a swimming pool. And, before you ask, no one seems to know what the origins of the name are, although a number of apocryphal stories can be found floating around the Internet. No one has been able to link the game of Marco Polo with the explorer of the same name, despite some creative efforts, and it is hard to determine when the first game of Marco Polo was played.

This game is probably an offshoot of blind man's bluff, a form of tag which is played on dry land. Blind man's bluff dates back to at least the 1500s, and it was once a very popular parlor game, especially with ladies. In both games, the person who is “It” must close his or her eyes, or wear a blindfold.

In the case of Marco Polo, all of the players are in a swimming pool, pond, or river. The person who is It, or Marco, depending on regional tradition, must find other players and tag them, using his or her sense of sound to detect other players. By tradition, Marco may call out “Marco,” and other players must respond with “Polo,” allowing Marco to locate them in the water. In some regions, if someone doesn't respond with “Polo” and Marco notices and correctly identifies him or her, they become It.

Once someone is tagged, he or she becomes the new Marco, and the game continues. There are also some variations which can be added to the game for additional interest. Under the “fish out of water” rule, if Marco suspects that someone is out of the water, he or she can call out “fish out of water,” and if the guess is correct, the unlucky player becomes It. In a related rule, if someone sits on the side of the pool with his or her legs in the water, Marco can call out “mermaid on the rocks,” and he or she becomes It.

This game is primarily played in the United States, Great Britain, and parts of South America, and numerous regions have their own unique variations of Marco Polo. Because Marco Polo is played in the water, it can be dangerous, especially for young children, and it is a good idea to have a lifeguard on duty. Sometimes the players become so caught up in the game that they miss signs of distress from other players, so having a neutral party to keep an eye on everyone is a very smart idea.