Dave--
Try contacting Dr. Barbara Purdy at Univ. of Florida Anthropology
Dept. (352-392-2031). She recently retired but they should be able to put
you in touch with her. She has recovered numerous prehistoric dugouts from
Florida wet sites and has worked on preserving them. She has also published
a book on wetland archaeology which might address the subject (Wet Site
Archaeology).
L. Wayne