According to the pilot, he was performing both water and pavement touch-and-go landings in his amphibious Piper PA-18A-150 in Gunthersville, Ala.
On final approach for a water landing, he observed a jet ski come out of a slew area and his attention was drawn to it.
Upon landing, “I found myself inverted,” he reported.
FAA inspectors responded to the accident site and examined the wreckage. The landing gear and the cockpit-mounted landing gear switch were found in the down (extended) positions. A cockpit placard was installed that stated “DO NOT LAND ON WATER UNLESS GEAR IS FULLY RETRACTED.”
The NTSB determined the probable cause as the pilot’s failure to retract the landing gear wheels prior to a water landing, resulting in a nose over upon touchdown.
NTSB Identification: ERA14CA431
This September 2014 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

It wasn’t the jet ski it was the scantly clad beauty riding it I’ll bet. I haven’t much time on floats and non on amphibious type. But, I flew hopped up Cubs on standard floats and only had problems remembering to retract the water rudders. When you get you feet kicked off the pedals on the takeoff because you hit small debris in the water you will eventually remember to retract them. You will always remember the limp you received from it, too.
Probable cause was that he didn’t retract the wheels AFTER TAKE OFF!
Amphibious training is severely lacking in this regard. Most do emphasize to check the wheels before landing on water or land, but that’s just a check, and it’s easy to be distracted, especially going into a lake. What is lacking in the training is that it should be a procedure that begins after take off. The small wheels on floats are not much good unless you’re on an improved surface and any off airport landing (other than a road) will have a better result with the wheels up.
Even if just practicing touch and goes at your local airport, remember it’s not just the landings you’re practicing, you should be practicing the whole procedure of wheels up after takeoff and then getting the gear down(in this case) for landing on land. Doing the whole procedure needs to become a habit and then followed up with a check of some kind, even if it’s just “GUMP” . . .