It's not quite water polo, nor is it a version of rugby played without shirts. In fact, Cuop Phet isn't even a game.
The Ball Scrambling Festival, as Cuop Phet is called, is held annually in Vietnam on the 12th day of the first month of the lunar year, which fell on Saturday this year.
Participants, like these men in Phu Tho province, compete to get the "Phet", which is a bamboo ball painted red to symbolise the sun.
It is believed that the person who manages to catch the ball will have all his wishes come true and will enjoy happiness and good luck for the rest of the year.
One troubling aspect of the festival in recent years - in a departure from tradition - is the violent clashes that take place during Cuop Phet.
Many young men, in their enthusiasm to get the ball and win some glory, take to using their fists to settle disagreements over who is the rightful winner of the Phet.
Unlike water polo or rugby, there appears to be no referee who can call out foul play.
These days, the police turn out in force to stop the event from getting out of hand during Cuop Phet. However, that doesn't appear to stop most people from having a ball.