Islands that appear and subsequently vanish because of the tidal effects are often associated with sea monster stories told by sailors. Vanishing islands are visible at low tide, but they disappear at high tide. The Philippines is home to seven of such islands while the San Juan Islands have several of them. In the medieval period, seamen created their explanations for the strange phenomenon. The explanations mainly revolved around large sea monsters which would accommodate a crew on its back before drowning it. Some of the sea monster tales associated with such disappearing islands have been described below:
The Tale Of The Merciless Aspidochelone
The tradition of the Physiologus, as well as, the medieval bestiaries mention the Aspidochelone as a fabled sea creature that is described in a variety of ways that range from a giant sea turtle and a huge whale to a sea monster sporting massive spines along the ridge of its back. Regardless of the form it assumes, the creature is described as enormous and it is sometimes mistaken for a rocky island complete with valleys, crevices, trees, dunes, and greenery. The term Aspidochelone combines the Greek word aspis meaning shield or asp and chelone meaning turtle. It was said to emerge to the surface from where it would attract sailors mistaking it for an island. After the sailors anchored, the creature would make a landfall on its large shell and would retreat to the depths of the ocean together with the ship and the people. Aspidochelone also lures fish populations with its sweet smell.
According to the bestiary and Physiologus traditions, Aspidochelone is portrayed as representing Satan who tricks those he aims to devour. This monster is called Fastitocalon in the Old English poem by the name "The Whale." The name Fastitocalon is probably a variant of Aspidochelone, and it represents the Devil. The poem's author remains unknown and it is among the three poems in the Physiologus or Bestiary included in the Exeter book. The Exeter book is accommodated in the Exeter Cathedral Library. The book, having undergone mutilation and translation, has some of its content missing or changed. In the account titled Natural History, Pliny the Elder describes an enormous fish which he calls Pristis.
The allegory of Aspidochelone is based on the description of whales in Etymologiae which was the work of Saint Isidore of Seville. Aspidochelone goes by different names in various cultures. It has been noted in traveler's myth and lore across Greece, the Latin World, Egypt, and Europe. A similar beast is included in the folklore of Greenland's Inuit societies as Imap Umassoursa. The beast was commonly mistaken for a flat island and sailors were forced to travel carefully around it. Another sea monster thought to be an island was Jasconius in Irish folklore. Another title used for Aspidochelone is Zaratan commonly used in the Middle East. Another massive sea monster is called Hide or Cuero in Chile. The monster is said to devour whatever it comes in its path, and it also lures sailors to their ultimate death.
Lyngbakr, The Monster In The Greenland Sea
A huge whale-like sea beast was presented in the Örvar-Odds saga as existing in the Greenland Sea. The saga described Lyngbakr as a heather-covered island which baited sailors only to sink into the sea together with the crew. The myth begins with a southwesterly journey of Örvar-Oddr and his crew across the Greenland Sea. As they sailed, they noticed two rocks jutting out of the water which puzzled Oddr. The crew later passed a heather-covered vast island. Oddr turned back and commissioned five men to check the island, but it had vanished. Vignir, the deck officer told Oddr that the crew would have drowned if they had landed sooner.
Hafgufa, The Monster That Ate Ships
The medieval Norwegian philosophical didactic publication by the name Konungs skuggsjá mentions the sea monster Hafgufa. In the written work, the King recounts to his son of the multiple whales existing in the Icelandic Seas. The King concluded by describing a massive whale that he was scared of but was uncertain if anybody else would believe him without sighting the monster. The King explained the Hafgufa as resembling an island than a living creature and added that it was rarely sighted and when it was sighted in same two locations. The King hypothesized that there were only two of them and that they must have been infertile else the seas would be inhabited by many of them. For feed purposes, the King explained that the creature would belch to expel food and thus attract fish. As soon as a large population had congregated in its mouth and belly, the creature would close its mouth. The Örvar-Odds saga notes Hafgufa as the mother of sea monsters whose food sources included men, whales, and ships. Hafgufa was believed to exist underwater only to emerge at night at low tide. The creature's nose and head would be the only physical parts that were visible.
The Legend Of The Kraken
As legend has it, a sea monster named Kraken exists off the coasts of Greenland and Norway. Over time, authors have postulated that the legend's origins lie in the sightings of giant squids capable of growing 40 to 50 feet. Kraken has been fictionalized in various works owing to its fearsome appearance and massive size. The English term Kraken originates from the Norwegian Krake meaning "something twisted" or an unhealthy animal. The term also means octopus in modern German. The author of Konungs skuggsjá (circa 1250) described the sea monsters sighted in a voyage across the Greenland Sea. The author suggested that there were only two of these beasts in existence which seemed incapable of reproducing.
The zoologist Carl Linnaeus accommodated Kraken as a cephalopod and gave it the scientific identity of Microcosmus marinus in the initial edition of his Systema Naturae in 1735. The creature was subsequently excluded in successive publications. Kraken was also noted in a publication by Erik Pontoppidan who was the bishop of Bergen. Pontoppidan claimed that Kraken was often mistaken as an island and that the whirlpool left in the creature's wake posed the greatest danger to sailors. The creature was also described by Jacob Wallenberg who was a Swedish author and Pierre Dénys de Montfort, a French malacologist. Kraken is commonly depicted as a massive Octopus-like creature, and its legend exists in today's popular culture.