The best way to ensure that audiences will get on board, as Nir has pointed out, is to make it about the struggle. There are a lot of films that focus on mankind’s struggle against unbelievable odds – Everest, 127 Hours, Touching the Void, Cast Away, Life of Pi, etc. etc. Usually, it’s not that important what the circumstances but the stakes have to be high – it’s about survival. The kid in your story can’t just choose to learn how to ice climb and find it difficult – he can quit at any time. Instead consider putting him in a situation where he has no choice because his life depends on it. A lot of the movies mentioned take experienced people as a means of highlighting the extremes – even the best of the best are struggling. So another option for you is to make him an experienced climber doing something that pushes him to his limit and beyond – maybe the protagonist is the veteran who has to go rescue the inexperienced guy like in Everest? Or he finds himself stuck somewhere like Touching the Void?

The other thing you could consider to help with marketing is include a location that even the average film-watcher has heard of. ?The Eiger, Everest, K2, etc, etc. By giving us a familiar name we immediately know the risks.

The most important thing for this kind of story though, in my opinion, is the stakes. He can’t have the option of turning back and his life has to be on the line. Get busy living or get busy dying!