An example of a wake giving the appearance of an undulating, serpentine animal. (Source)
Recently while out boating on Lake Erie with my family, I observed an interesting phenomenon which has received much discussion in cryptozoological literature. This was a standing wave or seiche appearing after the passing by of a boat, although the one which I spotted was on a less impressive scale than others previously documented. Described by biologist Dr. Roy Mackal as "the most ubiquitous of all the Loch Ness mirages," many cryptozoological researchers such as Dale Drinnon suggest that reports of alleged humps compared to strings of buoys and attributed to aquatic mystery animals are probable misidentifications of such wake effects. A variety of factors including boats and large marine animals can produce these wave phenomena, warranting the proposition of their role as frequent impetuses of 'megaserpent' sightings. Dale Drinnon reproduced my relaying of the experience to him, along with input regarding other cases of the effect, in an article which can be read here. Next time you are out on the lake, keep a lookout for this most intriguing aquatic occurrence.
Many reports of classic, sinuous lake or sea 'monsters' are probably not what they seem. Along with wakes, groups of known animals or an animal leaving a trailing wake may be interpreted as a monstrous unrecognized animal. Two examples of potential misidentification from the Frontiers of Zoology blog are reproduced above.