I was watching an old Navy movie today and there was a scene where these frogmen were on a rubber boat all geared up. They were rechecking their gear, listening to last minute instructions from their leader and waiting on the command to enter the sea. The command was given and each of them fell backwards into the water.
I though about this for a long time. Why did they all fall backward into the sea? Then it dawned on me, if the had fallen forward they would have all fallen to the bottom of the boat.