Oudemans' model from The Great Sea Serpent, 1892
The comparison to Oudemans' Sea Serpent from above and then a comparison to Sanderson's model in profile. Unfortunately, Sanderson does not provide a view from above for his composite. Except for the great length of tail allowed by Oudemans, the relative lengths of the head and neck, body and tail are all in the same general comparative proportions. The real differences are in the size and placement of the flippers and in the width of the body. Larkin seems to have exaggerated the relative widths of the neck and back to something approaching caricature. Below is the comparison to my composite model (Final composite, all Longneck sightings worldwide, final average statistics)
The Alvin (Submarine) one below differs somewhat in having a larger head and longer tail than usual, but these might only be false impressions due to poor viewing conditions. I do have one report of what sounds like a legitimate Plesiosaur-Sea-serpent corpse washed ashore and which was reported to me personally, and the witness said it looked like The Alvin Plesiosaur (Charles Berlitz got duplicate documents as stated on my copies)