Under the waters lies a plethora of beautiful, mystifying, and incredibly mysterious sea life. Animals never before seen or discovered are constantly being unearthed. One such example is the "immortal jellyfish", which has the amazing ability to cheat death by reversing its own life cycle and regenerating itself into a new body. Another animal that has captured scientists' imagination is called the "purple blob", which some describe as looking like a Christmas ornament. They are possibly, however, a newly discovered type of sea slug. 

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To this day, the mystery of the Mary Celeste remains one of the eeriest in nautical history. In 1872, the Mary Celeste travelled from New York to Italy but was later discovered abandoned in the midst of choppy waters. The British brig Dei Gratia had discovered it and had noted that only the lifeboat and the crew were missing. The cargo of the ship and a six-month supply of food and water were untouched. Many have speculated about what happened to the crew of the Mary Celeste, and why they had chosen to abandon ship. Theories ranged from sea monsters to pirates and even mutiny. Though no one can ever be sure, an article from the Smithsonian Magazine suggests that a faulty pump had led the crew and captain to abandon the ship before it sunk. 

The Kraken and the mysterious sea serpent of Daedalus—these are just a couple of the more renowned ocean mysterious that revolve around giant "monsters" underwater. 

The Kraken, which has long been part of Scandinavian folklore, finds itself thrust upon our reality with the discovery of the giant squid. This fierce creature truly lives up to its name, with the largest recorded one weighing nearly a ton with an impressive length of 43 feet. Though the animal itself is quite large, they're very rarely seen as their habitat lies in the inhospitably cold waters of deep-sea, anywhere between 1,650 to 3,300 feet below the ocean.

Giant oarfish have also been spotted on beaches and is the world's longest bony fish, with a recorded length of 56 feet, and weighing in at 600 pounds. They were first spotted in the 1700s, and no doubt were a fantastic mystery at the time. In fact, some wonder if the giant oarfish could have been the sea serpent spotted by the captain and crew of the HMS Daedalus in 1848. On a voyage to St. Helena, people on board had allegedly spotted a "sea beast" approximately 60 feet in length. It became a huge story in London at the time, and still remains a curiosity to this day. 

Atlantis has long been the topic of conspiracy. Though it's often attributed to Greek mythology, Japan has its very own mysterious "Atlantis" under its seas. The Yonaguni Monument, located beneath the waters of Yonaguni Jima, shows a mysterious pyramid-like structure that features defined lines and structural shapes that look like stone steps. Marine geologist, Masaaki Kimura from the University of the Ryukyus believes it to be the remains of a 5,000-year-old city, though Boston University professor Robert Schoch argues that the entire structure is natural and follows the "basic geology and classic stratigraphy for sandstones". Whatever it may be, it's certain that the Yonaguni Monument has captured the imagination of all the divers who have seen it for themselves. 

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