This is the king of all classic pool games. Long before schoolchildren learn about the real Marco Polo, a 13th-century Italian explorer who lived in China and wrote extensively about his travels, they are experts in this aquatic version of Blind Man's Bluff.
To play Marco Polo, you need at least two people, but it's better with a small crowd. One person is designated to be "Marco." That person must close his eyes and try to tag the rest of the people in the pool. To locate the other people, he uses a primitive form of sonar, yelling out "Marco!" to which everyone else must respond, "Polo!" Using the direction of the voices as a guide, the blind Marco lunges after his Polos. The first person to be tagged is the new Marco.
The rules for Marco Polo are pretty simple, but enforcing them can be tricky. The Marco might try to sneak a peek, or the Polos might not yell "Polo." In a classic jerk move, the Polos might even leave the pool entirely. To combat this trickery, some players allow the Marco to yell, "Fish out of water!" when he suspects someone of leaving the pool [source: Retroland]. If he's right, the "fish" becomes the new Marco.