Heuvelmans lists three opening categories:
1X) Vague or indeterminate reports, Mistaken observations and False reports or Hoaxes.
While I change the percentages of all the categories I allow those to stand, but I also add to the invalid reports the majority of the following categories:
2X) Super Otter 13 definite and 15 possible sightings. It has the overall shape like an otter, a serpentine body which undulates vertically, and a short or medium-length neck. The Super Otter may be about 65-100 feet long, sometimes reported up to several hundred or over a thousand (!) feet long. The creature seen by Hans Egede was probably a Super Otter, and it is perhaps a primitive archaeocete with four legs. As of 1965, the last definite Super Otter was in 1848, so it might be extinct by now.
The Report credited to Hans Egede (actually made by his son Povel) was most likely a misunderstood view of a whale now thought to be extinct in the area, and the Sundsland Fisherman report a more normal viewof another creature of the same type. The majority of the rest of the reports are mistaking waves in the water for living animals. As to the statement that the last one was seen in 1846, reports of the same type continue to the present day and it is permissible that NONE of these reports accurately describes any living creature. NONE of them would therefore be "definite" reports of a "Super-otter" or anything else.
3X) Many Humped 33 definite and 26 possible sightings. As the name suggests, this has several humps on it's back. It has a small head, short or medium-length neck, and (sometimes)a fin on its back as well as a pair of flippers. It seems to be about 60-100 feet long, and may be threatened or endangered, as there are very few recent sightings. It is probably an archaeocete.The Super-Otter and Many-humped categories are hard to distinguish from one another. Most of the reports in this category are also mistaken impressions of waves in the water, even if a Plesiosaur-shaped creature is making the wave. The distinctively black-backed, white-bellied reports with a back fin come from mistaken views of killer whales.
4X) Many Finned 20 definite and 6 possible sightings. This has a round head with whiskers, short neck, and many fins along the sides. It is probably about 60-70 feet long. The many finned seems to have some kind of armored protection, and seems to be another kind of primitive archaeocete.
Many-finned reports are most often mistaken views of several small cetaceans in a line. Some of the reports included are even Plesiosaur-shaped creatures or large whales. The Along Bay Dragons and Tompandrano do NOT conform to Heuvelmans' description.
1) Longneck 48 definite and 34 possible reports. The Longneck has a long neck, a humped back, and little or no tail. Some Longnecks have two horns, and the creature has a fast speed. The Longneck has flippers (similar to those of a seal) and is probably about 15-60 feet long. The Longneck is probably a kind of pinniped (seals, sea lions, etc) and the first known sighting was in 1846 (Although Heuvelmans states it was known to the ancients as "Physeter" and the first Sea-serpent listed on his table in the back is possibly a ?LN)
1A, Male of 1) Merhorse 37 definite and 34 probable sightings. The Merhorse has a head similar to a horse, a long neck, and a mane. It has big eyes and a snake-like tail. Sightings suggest that ther Merhorse ranges in size from 30-100 feet. The Merhorse's big eyes suggest that it may normally live in the deeper parts of the ocean.
Consequently the total numbers of reports in each category comes down somewhat owing to the mistaken reports being culled out. Both categories are still by far the majority of "Unidentified" Sea-serpent sightings, counted either together or separately.
5) Super Eel 12 definite and 11 possible sightings, equally well 12 larger and 11 smaller category sightings. The Super Eel may actually include different species. Most of them look like eels (the only sea serpents that actually are serpentine) though the description of their heads and coloration differ. Super Eels have large eyes and are said to be 20-100 feet long, in two bunches, one averaging about 30 feet and the other nearly 100 feet. Super eels are sometimes dying when at the surface, and are probably fish.
The larger and smaller size categories I name Titanoconger and Megaconger, and they differ in ways other than size. The Titanoconger is a really big deepsea, free-swimming fish marked with a distinctively darker back and lighter belly. I doubt if it is actually abyssal. The Megaconger is a smaller fish, although at an average of 20-30 feet long it is still larger than any known eel. It has a more even colouration and seems to favor shallower waters near to the coast and on continental shelves. Two subcategories in the Mediterranean and around Fiji might be more like large moray eels instead, without pectoral fins and otherwise similar to larger editions of the more common local morays.
Heuvelmans also includes a category of reports he calls ?LN?SE because he considers them difficult to categorize as either Longnecks or Super-eels. It would seem to me that about two-thirds of these are Longnecks and possibly a third (or less) are Super-eels: some of them are also reports of whales or other mistaken observations.
7x) Father-of- all-Turtles also known from only 4 possible sightings, is is described as a giant marine turtle. It may have some relation to the ancient giant turtle, Archelon. Heuvelmans considered the existence of the Father-of-all- Turtles to doubtful and the reports to be probably misidentifications.
8) Yellow Belly Known from only 3 definite, 3 possible sightings (as of 1965), this has a yellow color and is tadpole shaped. Its size is estimated at around 60-100 feet. Heuvelmans suggested that it might a shark or other fish, or even an amphibian[this last was the suggestion of the witness. I count it as a shark, much like a whale shark but with a longer tail and the markings run together to form stripes].Mackal subsequently tried to write off this category as sightings of marine invertebrates, but his arguments were flawed and he contradicted his own theory with other information elsewhere. In specific, he admitted that Salp chains were not known to come in that characteristic colouration.
Since I consider the basic creature described to be a kind of elongated shark, I also classify it loosely with the elongated basking sharks and even Eel-shaped sharks derived from reports of Seamonster corpses cast ashore periodically.