THE PILOT WAS LANDING AN AMPHIBIOUS FLOAT EQUIPPED AIRPLANE AT A SEAPLANE BASE ON A CROSS-COUNTRY CARGO FLIGHT. AS THE AIRPLANE WAS SLOWING AND CAME OFF THE FLOAT STEP, IT SUDDENLY SWERVED TO THE RIGHT. THE PILOT APPLIED FULL LEFT RUDDER AND FULL POWER TO CORRECT THE SWERVE AND SUBMERGED THE LEFT FLOAT. THE LEFT WING AND LEFT HORIZONTAL STABILIZER CONTACTED THE WATER. THE AIRPLANE WAS BEACHED AND INSPECTION REVEALED DAMAGE TO THE STABILIZER AND WING. THE PILOT HAD ACCRUED 30 HOURS OF FLIGHT IN THE ACCIDENT AIRCRAFT MAKE AND MODEL IN THE PREVIOUS 4 MONTHS.