large, old blanket for each team

Mark off the start and finish lines or use a gym and run to the far wall and back.
Give each team a blanket which is their lifeboat where they are safe from shark attack.
The teams need to race 'swim' to the finish line.
When the leader yells, 'SHARK!', everyone needs to get on the lifeboat as quickly as possible and stay there until the leader yells, 'ALL CLEAR!'

Score 1 point for the first team completely on their lifeboat and 3 points for the team that reaches the finish first.
Play a few rounds until the teams are tired out.