What are the physical and character traits of Brian that are helping him survive?

In order to survive throughout Hatchet, from the flight that results in a downed plane all the way to his eventual rescue, Brian demonstrates many physical traits and character traits that help him stay alive. One of the most important is his adventurousness, evident from the very earliest pages. He is on his own in a bush plane with a single pilot, traveling to spend the summer with his dad, and the pilot offers to show him how to fly the plane: “ ‘Here,’ ” he tells Brian, ‘put your hands on the controls, your feet on the rudder pedals, and I’ll show you what I mean.’ ” While Brian hesitates initially, his is more a token protest, and next thing, he has willingly “reached out and [taken] the wheel in a grip so tight his knuckles were white.” Nerves give way to interest and excitement in the face of the opportunity to fly the plane all by himself, especially after the pilot “let[s] go of his wheel . . . to show Brian he was actually flying the plane alone.” Had Brian lacked that adventurous spirit, his odds of survival in the wilderness would have been very grim indeed.
Two crucial physical traits are his stamina and his ability to swim, both of which are proven by the end of chapter 3, when he crash-lands the plane into the lake in the middle of nowhere, forces his way out of the plane, “out of the shattered front window,” and swims his way to the surface and then to the shoreline. Swimming is not necessarily a universally taught skill, but one without which Brian would have drowned in the lake in spite of his having successfully landed the plane. And the fight he put up to get out of the plane as it filled with water and struggle to the surface and then to shore proves his physical strength and stamina.
Finally, another character trait he evinces is his calm, collected head in the face of potential danger and the disaster he has suffered. He deliberately takes the time to sit down in the woods near the lake, empty his pockets, and take a thorough, considered inventory of what he does have (especially in comparison both to what he does not have and, particularly, to what he could have lost, beginning with his life): “A quarter, three dimes, a nickel, and two pennies. A fingernail clipper. A bill-fold with a twenty dollar bill . . . and some odd pieces of paper. And on his belt, somehow still there, the hatchet his mother had given him.” Further, he has his clothes and shoes, and a good head on his shoulders, and with those few physical items and his natural curiosity and sense of adventure, he makes it out of the crisis alive.