Obscure Mythological Water Creatures
Referred to by the Akkadians as Abgal and the Sumerians as Apkallu comes this vastly intelligent and civilized half-fish half man water creature. These creatures were said to have been sent by the god Enki (the Sumerian god of crafts, intelligence, and creation) to help civilize early humans by teaching arts and sciences that they themselves practiced. These amphibious merfolk would come onto land to teach humans during the day and then they would return to the waters to eat and sleep, sort of like a day job. The reason behind Enki sending these sculptors of man was that early humans were ignorant of the benefits culture and civilization. However once they Apkallu arrived humans learned crucial aspects of civilization such as writing, agriculture, city building, and law.
The Echeneis is of Greek origin and it is known to be a serpent no longer than six inches. It is often found clinging to rocks and annoying sailors to no end. While this serpent is said to be extremely tiny it apparently likes to latch onto the hulls of ships and bring them to a complete stop. There is no explanation given as to how something so small could stop something as big as a ship no matter what size the ship. Whether the Echeneis performs this task through sheer power or magical intervention it has also been known simply as "delay". They are said to live mainly in polar seas and this beast even has some historical renown. It is said that these beasts caused Roman general Mark Antony to lose a navy battle when a swarm of Echeneis caused his ships to become immovable. It sounds to me like everyone is using a six inch serpent as a scapegoat for poor naval decisions. A bit more on the magical side of things the Echeneis is known to be used as a love charm and that it can be used to stop fluxes of the womb in a pregnant woman to hold back birth until the proper time. Or if you need a spell to slow litigation in court this little guy is known for that to.
Echeneis Power or Magic
How do you think an Echeneis stops ships?
The Aspidochelone is a colossal sea turtle (or whale) the size of an island. Its name is a combination of the greek words aspis (shield) and chelone (the turtle). As this giant floats upon the surface mud and soil accumulates onto it's craggy back and eventually bushes and trees grow. This feigns the appearance of an island and when sailors make landfall and set up camp for the night some get quite unlucky because the beast may descend into the water and drown them all. This creature is even mentioned in the adventures of Sinbad from Tales of the Thousand and One Nights. It is also said to emit a sweet smell that lures fish into it's mouth, this smell could also be a warning to sailors to not make camp for the night on its back.
This deadly creature comes from Inuit lore. The Ugjuknarpak is portrayed as an enormous rodent that lives in the icy waters waiting for prey. Their skin is said to be extremely thick and tough to penetrate. It has a long and flexible tail that it uses to overturn kayaks as well as other small boats and grab people and pull them down to the depths where they are eaten. Some say that at the end of the tail is a hand which makes it easier to hold people underwater. It's prehensile tail makes it an extremely fast swimmer and a truly dangerous predator.
From European folklore comes the Jerruillette a half octopus half human that is reminiscent of Ursula from the little mermaid. The upper half is human and the lower half is octopus. They typically live in underwater caverns and sea caves at the bottom of the ocean floor. They pose no threat to humans because they are vegetarians and they primarily eat algae and seaweed. They are fond of shiny and pretty objects such as jewelry and sea shells and will adorn themselves with such objects. While they don't eat humans they will defend themselves if threatened and it is said that if a Jerruillette bites a human they will immediately turn to dust. However if a Jerruillette kisses a human then that human will turn into a Jerruillette and live the rest of their life in the ocean. They are extremely friendly to all ocean creatures and will use their magical powers to heal them if they are injured or sick. In 1756 in European ocean waters a ship was said to have sighted a Jerruilette. The sailors noticed a person in the water and thought that it may have been a person stranded at sea. The person started swimming away and the sailors gave chase only to be eluded as the creature descended to the depths revealing tentacles of an octopus to the sailors. I have to say that The Little Mermaid movie by Disney really made the Jerruilette look like an evil creature.