Charles Eagle's eyewitness sketch of his "Cadborosaurus" from 1933, with a pronounced underbite. This resembles the alligator with an underbite in the photo. Note: it is believed that some plesiosaurs had teeth that protruded out like those of crocodilians.
The head of the creature as shown does have that distinctive wedge shape that some plesiosaurs had, highest at the back of the head and tapering toward the snout:
And some scientists have suspected that the head of our surviving Plesiosaurs would have looked like this (They were classified together) This is speculative, however.
If the Caddy in question had a Plesiosaur's head, though, the opening in the back of the skull would be the Euryapsid skull openings, the eye sockets would be that other hump abut halfway along the length of the head. Mistaking the rear openings of the skull for eye sockets is a mistake which laymen frequently make.
The proportionate lengths given for this "Cadborosaurus" atre very like Oudemans' reconstructed sea serpent with its exaggeratedly long tail (Half of the full length) and this is probably due to a confusion with the wake. The thickness of 8 feet is very nearly doubled over Oudemans' version and so it is an independant indicator that the Vertical thickness was much exaggerated in this sighting.
It is notable that in this first Cadborosaurus sighting there is a spiny ridge down the middle of the back and not a mane as such.
Scott said the original source was Cadborosaurus: Survivor of the Deep. He also sends some other photo comparisons but in the non-Plesiosaur examples the head is too long and the wrong shape, and the length of the neck is much to short:
Vertical height decreased by one half and is much better in line with other sightings. there are a number of things which could cause this optical illusion but the most obvious would be confusion of the actual body with its reflection on the surface of the water. The inset drawing shows the head and the orange circle indicates where the eye should be (A number of sightings suggest the eyes are cryptically coloured the same as the skin but the Euryapsid opening in the top back of the skull might have false eyespots (Ocelli) that draw attacks instead of the real eyes.)