Underwater rugby is a sport where players wear snorkel gear and swim around underwater while trying to score a goal with a ball that is filled with saltwater so it doesn't float. The game is played at the bottom of a swimming pool or other body of water, usually about 3-5 meters deep.
The underwater rugby world championships are like a big tournament where teams from all over the world come together to compete against each other. It's kind of like the World Cup for underwater rugby!
There are rules that the players have to follow, like not holding onto the sides of the pool or pushing other players out of the way. The teams work together to pass the ball to each other and swim towards the goal, while also trying to defend their own goal from the other team.
It's really important to be a good swimmer and be able to hold your breath for a long time if you want to play underwater rugby. The game can be really exciting and a lot of fun to watch if you like swimming and sports!