Tug of war is a great way to introduce teamwork and competition, you can even have a 1 on 1 match.

The minnows line up on one side of the field to and attempt to run to the other side without getting their flags pulled by the sharks.

One kid starts the game as "it" and runs around the circle tags each kid with duck until they choose a goose. Once the goose is tagged, they attempt to catch the "it" before making it back to the gooses spot.