All you need for this game is a pool, students and beach balls!
Have at least 4 students, but no more than 20 (unless you are in an a much bigger pool). You’re gonna need some beach balls, too. If you have just 4 students, 3 balls will work. Try to maintain a “3 balls” to “4 students” ratio for this game. (For example: 6 students = 4 balls, 8 students = 6 balls, 12 students = 9 balls, 16 students = 12 balls, and 20 students = 15 balls.)
Now, have everyone except one student, deemed the “Monster”, go to the same end of the pool. Give the Monster the beach balls based on the ratio of students above.
The purpose is for the students in the pool to make it to the other end of the pool without getting hit by the balls the Monster is throwing at them. Tell them GO! The students then must swim to the other end of the pool. If they choose to swim underwater, they have to surface at least two times – this gives the Monster a fair chance as he/she throws balls at the students.
Once the Monster throws all of the balls, he/she can’t get them out of the pool until everyone gets to the other end of the pool. When the Monster hits one of the swimmers with a ball, the swimmer must get out of the pool and become a Monster in the next round, and help the current Monster/s in the next round. Play until there is only one student left in the pool, and that person is the winner.