Hey DIED, just saw your post, sorry I didnt answer you sooner.
Dang wear burnt up my chain saw cutting those trees down.
The trees looked like oaks but I am not 100% sure, All the bark and most limbs were gone. We have mostly oaks and sweet gums in this bottom.
They extended above the water, full height in about 4 - 6 feet of water.
My wife "didnt like the look". !@#$% So I cut them to be submerged by about about 2 - 3 feet at full pool. : )
Tim, that is one heck of a fun looking treehouse - any way to add a zip line? Wow that would be a hoot. I guess getting back and forth would present logistical issues...better yet - electricity. Heck, with a fridge you could last quite a while out there. Cant wait to see tree house above full pond.