Adult learners are more able to draw on their previous experiences of similar activities, allowing them to make connections between what they are doing and what they have done in the past, and in doing so pick up things quicker. Children naturally don't have as many previous experiences to draw on so are less able to make those connections. Also, adults tend to think about what they are doing more, and the theory behind what is happening, whereas children don't. Children don't really care how they are able to float as long as they can float, whereas adults want to know why. Finally, in my experience, children are far better at copying actions than listening to explanations of what to do. As such when I'm teaching children I spend a lot more time demonstrating the movements, whereas with adults I can generally just tell them what to do, explaining the reasons behind it and they will get it.