In general, this has been my impression as well. What I'm finding though is that the interweb (even google scholar) doesn't seem to be the place to get a definitive answer. ?
And... now I've forgotten where I was going with this... ?
I wasn't completely joking, but I could just put him in slowly in water (while keeping my hand under him) and see if he swims, I'm not saying to just throw a cham in a bathtub and see what happens... In the name of science! Doesn't seem too bad when scientists shake branches with sleeping chams on them.
Exactly what I'm saying, no need to actually leave the cham there long enough for it to sink, just enough to see if they can swim or not, like 5 seconds in the water is all needed to tell.
I actually have seen one of my past Furcifer pardais swim in my God Fathers Koi Pond. There was an island with tree's and my Ambanja was wanting to go to the other side. The Pardalis went without hesitation into the water and swam to the other side. I think chameleons do not have to worry about sinking. When they swim they inflate their lungs (that are huge for their size) and float. Then they swim similar to a snake with their tail and paddle with their arms in legs as seen in the video posted on this thread.