Ryan,
I'm not exactly clear with your question, per se. I'm guessing that he just gave it the power required to get off the water and rotate and then just slowly and gently climbed. Like I mentioned at the beginning of the video, a forest fire destroyed everything in the area so there aren't too many trees left in the area, except for an an occasional standing burned one, so no trees to really worry about. (Even in un-burned areas the trees there are pretty scrubby and not too tall to begin with (jack pines.) The terrain is pretty flat as well so there's lots of room for a gentle climb without hitting a hill. Then add to that, the lake had plenty of room to work with. It's was similar to the takeoff in the video clip where after we unloaded and the other guys flew out. Plenty of room and just a nice gentle vertical climb speed. I imagine where you live it could be pretty different because of the all of mountains and valleys to contend with.
One final comment is that there were 7 of us, plus the pilot, and we were probably about 750 lbs or so under the allowable weight. Even with th power and STOL capabilities of the Otter it still took a while to get airborn. Then again, I'm sure the pilot was only using what was necessary to get us off the water in order to conserve fuel and go easy on the engine. Also, it was the first time that he'd flown into Lake Clarkie and he was super extra careful in taxing to the dock because he wanted to make sure that there were no rocks just under the surface. He probably landed a good mile away and just crept to the dock. I was in a Cessna bush plane once and the pilot wasn't familiar with the lake (much smaller) and he and circled that thing about 5 times to check it out before landing. There were some gas cans in the back that were fumy smelling and when he sharply banked as he circled around, I almost lost my breakfast between the steep bank and smelling the fumes.
Hope that answers your questions (and then some!)
Steve