The pilot was taking off on a glassy water lake, in a float-equipped airplane. While on step, the airplane veered sharply to the right toward the nearby shore. The pilot said he tried to return to the departure heading using rudder and aileron, but the right wing encountered heavy brush, which caused the airplane to turn to the right toward the shoreline. Realizing he was going to hit the shore, he closed the throttle. The airplane received substantial damage to its wings and fuselage. The pilot said he did not know what caused the initial course deviation, but speculated he may have encountered something hidden under the surface of the lake. A certificated aircraft mechanic with inspector authorization examined the airplane after the accident, and said he did not find any flight control or rigging issues that would explain the initial course deviation.