In previous posts I mentioned that the Patagonian otter, the huillín could be mistaken for a lake monster by an inexperienced observer.
Their wet fur looks like scales when wet (otter photograph).
And a group of swimming otters may look like a long undulating lake serpent. The following sketch explains this monster-otter likeness.
I stumbled across the following photographs, which I reproduce below (my thanks to David and Melanie). They show a group of otters (the giant Amazon otter) swimming in a lake.
The uncritical observer would say that the upper photograph shows a long sleek lake monster.
 Gould, R., (1976). The Loch Ness Monster and Others. Secaucus: Citadel Press. pp. 116.
 Radford, B. and Nickell, J., (2006). Lake monster mysteries: investigating the world's most elusive creatures. University Press of Kentucky. pp. 118.
 The images are copyright © by David and Melanie's Trips. Yasuni Wildlife.
Copyright 2009-2010 by Austin Whittall ©