Traditional water fights have squirt guns or water balloons that take time to fill and slow down the action.
Here is a suggestion that will speed up the action.
Use sponges.
Take about 50 to 100 hand size pieces of foam rubber.
Place 1/2 dozen full buckets of water around the area.
Let the action begin.
Scouts are not allowed to pick up the buckets, but can quickly fill their sponges.
Scoutmasters quickly become favorite targets.
Note there is no litter of broken balloons to pick up and no “arms race” advantage to people with more expensive squirt guns.