Brian Robeson is lost and alone in the mosquito-infested Canadian wilderness. The bush plane he was flying in to visit his father lies at the bottom of a lake with a dead pilot inside.
Brian bumbles along the first few days after the accident and then experiences his ultimate low point when he sees a search plane but the pilot doesnʼt see him. After a failed suicide attempt Brian starts to embrace his situation.
You go from "bumbling" straight to a suicide attempt? We need a better sense of the despair that Brian feels to make suicide acceptable so soon in this synopsis. Perhaps it's best not mentioned here.
Armed with only a hatchet, Brian figures out how to make fire and procure food. He has way more setbacks and frustrations than successes but by not counting on being rescued Brian embarks on a life-path of survival as he physically, emotionally and spiritually becomes a part of the wilderness.
"Way more" is stylistically out of character for the text you're describing. Your synopsis should reflect your text whenever possible. Also: "life-path"? This sounds like new-age bibble in the face of a story about survival in the wilderness.
When rescue finally comes he meets it not as a scared, helpless kid but as a mature young man at home in his body and surroundings.
There's clearly the seed of a good survival story here, but there are enough inconsistencies in the way this synopsis was written that I think I would pass on seeing the manuscript.