Thread drift, but a little, I suppose....
"I was having him land me into the dock."
I wanted him to have docking practice, and I wanted to get out on the water, so he could fly his required five solo water circuits for the seaplane endorsement.
When you say 'touch the keel', can you confirm your meaning of that and clarify if that is a good thing or a bad thing.
Good thing. Unlike floatplanes, flying boats are landed on the step, much like a wheel landing, so it is entirely possible, and desirable, to touch the keel and then allow the plane to slow, and settle into displacement at about that pitch. Stall landings work too, but are much less graceful. OTOH, landing a floatplane on the step is courting disaster.
What did the student do that was wrong.
Truthfully, I don't really know, but I'm guessing it was about what is depicted in the video, though water conditions were just a light ripple, so it wasn't waves causing porpoising. My mind chooses to not recall a rather violent ride, and I'm just fine with that, so I cannot describe the rest of the coming to a stop. Flying boats are wonderful on the water, much more maneuverable, and mishandling tolerant than floatplanes, but do require a precise touch, and are prone to porpoising if it is allowed to continue.
To the topic at hand, I had a super student, with great attitude, an attentive desire to learn well, and decent experience on type - and between us, we still got it wrong. I have also started to train a Lake owner with zero time on type, really poor flying skills, and a less than ideal airplane (no shoulder harnesses at all installed). After some runway training, then more, and more, and more, totaling 60 circuits over two days of training, I never reached the point where I would ever send him solo (in any plane) on wheels, much less on the water. I never landed him in the water, and told him that I would require more basic training on wheels for him, before I would return to train him. My challenge was that he had paid my expenses to fly literally across Canada to train him, and now I would not - and I did not. Someone else did, as I have heard tell of scary GoPro videos, attributed to him. Nice fellow, but inadequate hands and feet skills, and precise flying skills to enter into water training with me. I could not convince him of this, as his flying school (I met some of them) kept telling him how great a pilot he was.
Student attitude makes a huge difference in train outcomes, and behaviour post PPL. Human factors tries to open this topic, but its the instructors, school operators, and onlookers (like PPR Aerodrome Masters) who have a role in identifying poor attitude pilots, and perhaps mentoring - But, I agree, a few people just won't listen....