This is a mini-game i created called island boxing
Step 1: Body of Water
Find a reasonably large body of water to make the mini game
Step 2: Rectangle
Build a large rectangle in the water out of a block of your choice
Step 3: Teams
Add 3 blocks on each side of red and yellow although it doesn't really matter. Make sure the team blocks are a different colour than the middle
Step 4: Get Some Friends
Get some friends to play with. You can only play with two people at a time but you could do a mini tournament.
Step 5: Rules
Each player starts at their end when the referee says go they both start punching each other. The person to fall into the water wins.
Step 6: Alternate
Alternatively you could do it on land and around it put lava to spice it up a bit.