On April 27, 2012, about 1644 central daylight time, an Aviat Aircraft Inc. A-1B, N388AS, was substantially damaged following a loss of aircraft control and collision with terrain near Sylacauga, Alabama. The certified flight instructor was not injured and a student pilot had serious injuries. The airplane was registered to a private individual and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated at Alabaster, Alabama, about 1330. According to the pilot, he landed on the water at Lay Lake on a southwesterly heading. He then attempted a takeoff. During the takeoff sequence, he raised the left float off the surface first. The airplane began to climb, but did not accelerate as expected. He attempted to maintain wings level; however, the right wing "fell." As he attempted to recover from the stall, the airplane impacted the terrain. A Federal Aviation Administration (FAA) inspector responded to the accident site and examined the wreckage. Flight control and internal engine continuity was established. The magnetos were rotated by hand and produced spark on all leads. The landing gear floats were dry inside. The wreckage was moved to a storage facility in Clarksville, Tennessee. The wreckage was examined on May 29, 2012 by the NTSB Investigator-in-Charge (IIC). An external inspection of the engine revealed no damage to the case or cylinders. The spark plugs and ignition leads were re-installed and the starter was activated with an external battery. The engine turned through several times and no unusual noises or binding were observed. An engine run was not attempted due to impact damage to the intake system. The lower spark plugs were removed and the engine was manually rotated with the propeller. Valve action on all four cylinders was correct and compression and suction were observed using the "thumb" method. The spark plug electrodes were normal in color and wear with the exception of some light rust on some surfaces and the plug threads. The fuel strainer was removed and the screen was clean and unobstructed. About 1 ounce of a substance that resembled brown mud was found in the bottom of the strainer bowl. The carburetor was removed and opened and the accelerator pump operated normally. All carburetor control linkages were intact. The venturi was intact and in place. The white plastic floats were uncompromised and empty of fuel. The carburetor bowl contained about 3 ounces of muddy water with an odor of 100 low lead aviation fuel. An examination of the cockpit revealed that the carburetor heat knob was in the "hot" position. The knob was bent by impact forces and could not be moved. The FAA inspector provided the NTSB IIC with a video of the accident sequence. The video was produced by a local witness. A review of the video showed the airplane taking off and entering a gradual, right-hand turn. Trees and terrain were visible at the boundary of the lake. The airplane disappeared behind some trees and the sound on an impact was heard. Engine noise was apparent until the sound of the collision was heard. The Aviat Husky A-1 "Before Takeoff" checklist, step 13, states, "Carburetor Heat – COLD."