Spectators, officials of some sort of course, and they are skiing into water. The skier would be a participant in an event that looks like it includes judging which may lead to skiers skiing backwards.

Even if it doesn't the skier is a participant. Participants are not normally going to be held liable for acts while competing.

Who could be liable? The event organizer or so the ski resort or both. Who set up the barricades us going to face the biggest exposure.

The skier least of all. If it wasn't an event and he is just on the mountain that is different but it is clear he is at some organized event.