1. The problem statement, all variables and given/known data Blobbing is one of the extreme attractions in aquaparks. A person is lying on a big raft positioned on the surface of water and filled with low-pressured air. Another person jumps down from a given height onto the opposite end of that raft, throwing the lying person in the air. It is estimated, that the loss of energy is approximately 35%. How would the energy loss change if we were to move that raft from water onto concrete? Justify your answer. 2. The attempt at a solution In the presented position, there is an upthrust, pushing the raft out of water. What follows is that when you jump onto that raft, the energy you add to the system will be used for the attempt to push the raft deeper in the water, but this will be balanced, because the volume inside water will increase. Thus, if we were to move this raft to concrete, when the jumper would hit the surface, more energy would be used into throwing the person in air. However, I am not sure of my explanations and I would be glad if you could advise me.