Yes, you are correct.
Mention has been made of the trim tab. Yes, it was in the full nose - up position. The flaps were also in the full up position. The flight manual calls for flaps to be down for all takeoffs and landings. Operating speed limitation is 125mph. Both the 200 HP Buccaneer and the 250/270 HP Renegade take off from land or water at about 60 mph. The flaps are set at 20 degrees and are slotted, low speed-high-lift and are about 14 feet in length and when they are extended down and rearward, practically double the lift of the wing. The nose tends to go down with flap extension, hence the use of up trim.
If flaps are not used either intentionally or the pilot forgets them, the aircraft flies very much differently. The speed at lift off is now raised considerably and should the pilot try to rotate the attitude for what he believes to be a normal flaps-down takeoff, the result is now a very nose high attitude exacerbated by full up trim and wave action. It takes a super pilot to realize what is happening at this point.
Lake pilots are taught a correct attitude for take off which is just slightly nose high which allows the speed to build to takeoff speed without any obvious "rotation" at lift off, and this should happen around 60mph in a fairly flat attitude. If one pulls the nose up during the takeoff run, the tail goes down and the speed reduces and it also gives the wings an angle of attack, however that slows the aircraft further, resulting in no lift-off.
Lake trimming is different from any other system. Because it is a pusher it requires lots of up trim at full power, but we also have to trim it for a glide also, which has a total lack of thrust. We have to trim it differently for the load it is carrying in the cockpit, all forward of the center of gravity. We have to trim it for water step taxiing and lift-off speeds and in between. The trim differs from model to model, whether it is a 150HP C-1 Skimmer or a 270HP Renegade. My Skimmer #1 has a trim tab on each elevator similar to most aircraft built in the 1940s. I have lots of time in other C-1 Skimmers with 150 horsepower and there was enough trim. However, Skimmer One now has 160HP and the same trim system, which is barely adequate, depending on the load. I now have to have the elevator full up for a step taxi and liftoff, due to the nosedown thrust. Reducing the throttle slightly helps.
So you see, it is a fairly complex arrangement to cover all the attitudes, power settings, loads, drag of the water.
After having said all this. The problem is usually the pilot forgetting a checklist and leaving the flaps up for a water takeoff and then trying to fly the machine as tho the flaps were down. An excellent reason for leaving the flaps down when parked on land or water....lest we forget....it is a different airplane without them.