What are Lake Monsters and Sea Serpents?

A popular theory among Cryptozoological investigators is that aquatic monsters, mainly sea serpents an lake monsters, are surviving plesiosaurs. Plaseiosaurs are known to have lived in the oceans(and possibly lakes) of the world in the age of the dinosaurs. They had large bodies, short tails, long necks and small heads, and four flippers. But, I you read about lake monsters and sea serpents, many do not sound like surviving prehistoric marine reptiles.
The Loch Ness Monster as a plesiosaur

Many people have many different theories about what these animals are. Some, like I said above, really do think most lake monsters/sea serpents are plesiosaurs. I also thought that for a long time, but do not anymore.

Early Nessie investigators, like R. T. Gould, thought the monster could be some sort of gigantic newt or salamander! Tim Dinsdale believed the monsters were plesiosaurs. Dr. Roy Mackal first thought it could be a giant water slug, but afterwards changed his mind and thought the monsters could be some sort of huge amphibian or giant eel. F. W. Holiday believed the creatures were similar to the Tully Monster, an very strange prehistoric creature. The Tully Monster, however, only got to about 14 inches long, and Nessie is usually said to be 15 to 30 feet! He later thought that the monsters were connected with UFOs! On the documentary The Loch Ness Monster Revealed, the seekers came up with a theory that Nessie could be some sort of animal that looks like a plesiosaur/turtle. A witness who saw Nessie in the 1930s said it looked like a "camel-horse!" (More on that sighting can be found in an earlier post.)
R. T. Gould
Roy Mackal
Reconstruction of the tully monster
F. W. "Ted" Holiday
Roy Mackal(left) and Champ researcher Joe Zarzynski

Champ researcher Dennis Jay Hall believes the creatures in Lake Champlain are Tanystropheus, and even has a name for his creature: Champtanystropheus.
Hall's Champtanystropheus on the 2003
documentary America' Loch Ness Monster

Bernard Heuvelmans, the "Father of Cryptozoology", believed there were several different kinds of sea serpents, and these could also account for lake monster accounts. He believed there were:

  1. A long necked, tailless mammal
  2. The merhorse
  3. A short necked mammal, with many humps and one pair of flippers
  4. A mammal with many triangular fins
  5. Something that looked like a giant otter
  6. An enormous crocodile
  7. Giant turtle
  8. Giant tadpole
  9. Giant eel
Bernard Heuvelmans,
the Father of Cryptozoology

Heuvelmans' book In the Wake of
the Sea-Serpents

Some people think cryptids, like the Mokele-Mbembe, seen in Africa could be surviving dinosaurs. The Mokele-Mbembe is commonly seen in water, so many classify it as a lake monster.

Other lake/sea monster researchers think the creatures are some sort of pinniped, like a giant, long-necked seal. This is the theory I think is correct, after reading many accounts of Scotland's Loch Ness Monster, that certainly sound like a mammal, and not a reptilian plesiosaur. It is also the theory in Peter Costello's great book In Search of Lake Monsters, which I will review on here in the near future.
Peter Costello

Costello's book, showing Nessie as
a long-necked, seal-like mammal,
probably what it actually is


What do you think lake/sea monsters are? Do you believe any of these theories? Are some of them totally nuts? (Yes!) Do you have any different theories? If you do, please comment, I'd love to hear them!