This might be a rather silly rule to say when you are on the wild rapids but it will be better and safer to stay on the raft at all times. This doesnt necessarily mean falling out of the boat (because everyone has a chance of falling out) but it applies more to being silly by leaning out of the boat, grabbing objects in the water, standing up or sitting on other people. This all puts you in a dangerous position to fall out of the boat and can also make the raft wildly unstable which can lead to everyone either losing control of the raft or the raft tipping over and everyone getting soaked. When you fall out of the boat, everyone in the raft has to stop or slow down the raft so you can get close and get in the raft. you can also get caught under rocks or in a tricky situation that can put you in a lot of danger.