I did the HUET a very long time ago - before it was called that. Though I am confident in the water and at the time was an occasional SCUBA diver, it was scary enough.
But I thought more applicable to a helicopter going into the drink than what I would expect for a fixed wing ditching.
I did a couple of deliveries with a ferry pilot who had ditched several times. As I recall, one was a high wing Cessna which went nose down and stayed semi submerged supported by the wing for a while. The problem was, that as he exited from the door (which he had the good sense to have cracked open before impact), he got trapped by the fully extended flap and had to dive down and back to get clear. He was not too far offshore so the US Coastguard got to him in a helicopter.
Another was a Chieftain which (lucky for him) had the optional crew hatch on the left side of the cockpit. He went in under full control and said the touch down was gentle enough. He had time to open the hatch, grab the small liferaft stowed on the co-pilot seat and get clear. By the time he got in the raft the aircraft had disappeared. From memory he was rescued by a Russian ship and ended up in Vladivostok.
What nearly did for him was a BN Islander. The sea was calm enough and touchdown very slow. But because the fixed nosewheel dug in to the water, the nose section crumpled backwards and smashed his legs. When I last saw him he was still using walking sticks.