The pilot's improper decision to continue the flight rather than making an immediate water landing due to the low altitude of the airplane and obstructions ahead, which led to his intentional maneuver to avoid the obstructions and subsequent inadvertent stall and loss of control. Contributing to the accident were: an inadequate 100-hour inspection of the airplane by company maintenance personnel for failure to fix a damaged ignition lead and a partially separated keel on one of the floats, the pilot's inadequate preflight of the airplane for his failure to pump a float to remove water, and the pilot's intentional operation of the airplane with an excessive magneto drop.