what obstacles that nearly stop brian from getting the survival bag from the plane

The next morning it takes him nearly two hours to swim to the plane with the raft. He is exhausted when he reaches it, and stops to think about how he could get inside the plane, when all of its openings are underwater. He hits the body of the plane in frustration, and to his surprise the aluminum covering easily gives way. Sensing an opportunity, he takes his hatchet and cuts through the aluminum, trying to make a large enough opening for him to fit through. It is going well until he accidentally drops the hatchet—his most precious tool—down to the bottom of the lake.

He screams in anger but stops himself, because that sort of feeling sorry is something the old Brian would have done, not the new one. Instead, this new Brian dives down into the lake to try and get the hatchet back, more than fifteen feet down. He tries multiple times, and finally dives deep enough to fetch the hatchet from the mud. Out of breath, he tries again to hack a hole in the plane's fuselage to get through. After a lot of work he makes a space big enough for him to wiggle through.