Running a water fight is a great summer event which is perfect for your teens to invite friends to.
If you are going to run a water fight make sure you allow at least 2-3 days prior to the event to fill up water bombs as it can take a long time to fill up enough water bombs to make it epic.

See the pictures below as a point of reference for setup ideas. Take special note of the water bomb slingshot pictured below. The best rubber to use for a slingshot is “speargun rubber” from your local rubber store or on eBay. It costs (approx.) $15 per meter and you’re going to need around 4 meters per slingshot but it is definitely worth the money. Run a 2-meter length on each side folded over on its self (making it 1m on each side). For the launching pouch, you can use a plastic cup. Simply attach a plastic cup big enough to hold a water bomb to the end of both pieces of rubber.
Note: Using multiple cups stacked in on them selfs (making it a triple layer cup) can help make the cup stronger when you try to pull back on the slingshot.