In article .com,
"Doug" wrote:

Amphib nosewheels don't fully retract inside, but they do go up.
Notice the mains are down also.

HE FAILED TO RAISE THE GEAR!! That's why he flipped over forward!! The
nosegear was down and caught the water and flipped him forward.

Actually, the drag of the mains pitched him over; the nose gear just
finished the job.