4 buckets of water or more depending on number of people
Fill four buckets with water and place them about 10 feet apart in a straight line. Put a t-shirt in each.
Divide the group into four teams, and have each team line up across from a bucket, about 30 feet away.
Once the race begins, the first member runs to the bucket, puts on the wet t-shirt, and runs back to his/her team. When he/she reaches the team, he/she removes the shirt and gives it to the next person.
The next person runs with the shirt in hand to the bucket, dunks the shirt into the water, and puts on the wet shirt.
The first team to have all players finish the task wins!