The pilot reported that, during approach to the 765 metre wet grass strip, the wind appeared to change to a tailwind. The mainwheels struck a concrete sea wall which marks the threshold, both tyres burst and the landing gear legs were damaged. Directional control problems were experienced during the landing and a go-around was carried out, with the aircraft becoming airborne just before the far end of the strip. The pilot was not aware that any damage had occurred until the gear would not retract. A diversion to an alternate aerodrome was conducted and the left main gear leg collapsed on landing. The strip at the original destination was too short for normal operation of the heavily laden aircraft. Because of this, and the wet surface, the pilot had approached at a lower than recommended airspeed, aiming to land close to the threshold. He had been unable to arrest the sink rate which developed in the final stages of the approach.