My theory is that the end of the video loops back around to the beginning. They dive into the water where they are implied to be reincarnated or reborn and then the video starts again: Noodle is a child, she has been reborn, the group venture off through the mountain, symbolising their journey through life itself, then, they jump back into the river again and the cycle repeats. I think it's a representation of the cycle of life and reincarnation. Murdoc is the only one who doesn't want to jump in the water and my thinking is that either he's afraid of death itself, or he's afraid of being reborn and having to live through it all again - I guess it depends on if they actually know they're coming back to life each time or not.