According to the pilot, he was making a water takeoff from a finger of a lake that extended into a narrow canyon. During the takeoff run, he was almost on the step when the right float struck a submerged object. He aborted the takeoff by reducing power. The airplane drifted to the right, and the right wingtip contacted the canyon wall. The airplane pivoted to the right, the right float contacted the canyon wall, and the airplane came to a stop. The right wing sustained structural damage.