When you land your boat flat off a waterfall that’s higher than 20 feet—rather than diving the nose of the boat beneath the surface—the tension of the water doesn’t break. You can compress your back and break vertebrae. With higher waterfalls, even if everything goes right, you can break bones.
In 2011, Coombs broke two ribs and punctured a lung while making the first kayak descent of Oregon’s 96-foot Abiqua Falls. He still considers it a successful descent.