THE ACFT LANDED AFTER A PREVIOUS FLT & WAS REFUELED & PREFLIGHT FOR ANOTHER MISSION. ACCORDING TO MAINTENANCE PERSONNEL, THE ACFT FLOATS WERE DRAINED ONCE EVERY MORNING BEFORE THE 1ST FLT OF THE DAY IN ACCORDANCE WITH THE MANUFACTURER'S RECOMMENDATIONS. THE PLT STATED THAT WHEN SHE WAS TAKING OFF FROM THE SEAPLANE BASE, THE FRONT RIGHT DOOR WINDOW BECAME OPEN & SHE LEANED TO THE RIGHT TO CHECK THAT THE DOOR WAS CLOSED & LOCKED. SHE CONTINUED THE TAKEOFF. WHEN THE ACFT BECAME AIRBORNE, SHE HAD TO HOLD AN ABNORMAL AMOUNT OF RIGHT AILERON TO HOLD THE WINGS LEVEL. AT THAT TIME, SHE NOTED THAT THE ACFT WAS NOT ACCELERATING & CLIMBING PROPERLY. THERE WERE HIGH TENSION WIRE AHEAD, SO SHE ELECTED TO ABORT. THE ACFT WAS BANKED TO THE LEFT & WAS LANDED HARD WHILE IN A LEFT WING LOW, FORWARD SLIP. THE FLOATS SEPARATED, & SUBSEQUENTLY, THE ACFT CAME TO REST IN ABOUT 4 FT OF SALT WATER. NO EVIDENCE OF A PREIMPACT FAILURE WAS FOUND EXCEPT THE LEFT FLOAT HAD 3 POPPED RIVETS & A QUANTITY OF WATER.