Jump 50ft in the air, do some flips and twists and touch down lightly on a small landing area. Aerial Skiing, as discussed in the video, is about adding extra layers of complexity onto existing movements (double to triple backflip). The high level athletes in this video are seen doing basic mobility and agility drills, all to help with their body awareness in the air. They talk about quality over quantity, especially at such a high level and how half of their training is dry land.
Note: I'm thinking that keep the water choppy at the bottom is a good idea.