Hi Wayne. I think it is a great idea to use monochrome to capture the architecture of the mangroves, and I think the sepia is an excellent choice. It does look to me as though the highlights are blown, though I haven't downloaded it. However, I would be prepared to sacrifice some more detail in the dark areas to increase impact.
I like the way the large tree on the right anchors the image and that the center of the image draws the eye all the way to the rear.
The diffuse lighting is nice in that strong shadows cast by every root would be very distracting. However, it also leads to a lack of detail and wonder if you could bring out some of the texture out using Local Contrast Enhancement. Maybe slightly increased contrast would help. Perhaps the lack of detail on the tops of some roots leads Dave to thinking that there are blown details, though I don't see it that way.
Good attempt... I know I really struggle with mangroves too... I love the way the morning light at dawn really makes them glow but I've yet to find a composition that does them justice.
I like that you've used tele to try compress them, and I like the dof to the rear, but I find the foremost root coming in from the left that isn't in sharp focus distracting, it tends to keep leading my eye out of the left side of the frame.
Your second version works far better for me, Wayne. It's very nice. Consider using less of the gold tone and more of the reddish brown tone. Also consider converting the second version to black-and-white.
I agree with both Wayne and Trace - Mangroves can be a real challenge to photograph and to capture their striking appearance. By using sepia you have managed to minimise tangle of distracting elements. I am thinking of trying night photography and illuminating the convoluted root structures with a single flashlight. Hopefully I will post the result soon but if you don't hear from me you will know the crocodile got to me first.
Grant