A huge mass of granite found on the seabed off the coast of Rio de Janeiro, suggests a continent may have existed in the Atlantic Ocean, drawing quick, though largely symbolic, comparisons to the fabled lost city of Atlantis.

Finding granite more than 8,000 feet beneath the sea is remarkably unusual because the rock is formed on dry land, said Roberto Ventura Santos, director of the Geology Service of Brazil (CPRM).

"You don't find granite on the seabed. It is more usual to find it on the mainland," Santos told the Brazilian newspaper Estadao, according to The Telegraph.

"This could be Brazil's Atlantis," he said. "We are almost certain, but we need to strengthen this hypothesis."

Greek philosopher Plato wrote about Atlantis, a lost metropolis beneath the sea, around 360BC. But the comparisons to the lost city are mostly symbolic. Ledgend has it that before Atlantis sunk into the sea some 12,000 years ago, it was home to a highly developed civilization. No trace of the city or the people who lived there has ever been found.

The latest underwater exploration found no evidence of man-made structures.

"Obviously, we don't expect to find a lost city in the middle of the Atlantic," said Santos. "But if it is the case that we find a continent in the middle of the ocean, it will be a very big discovery that could have various implications in relation to the extension of the continental shelf."

The granite slabs were found by a submarine vessel combing through relatively unexplored waters about 900 miles off the coast of Rio de Janeiro.

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) operated the Shinkai 6500 manned submersible that made the discovery possible, but the Japanese have been downplaying any comparisons to Atlantis.

Shinichi Kawakami, a planetary science professor at Japan's Gifu University, told the Japan Times the granite could have been a part of a big continent before it separated into what is now Africa and South America.

"The concept of Atlantis came way before geology of the modern age was established. We should not jump to the Atlantis [conclusion] right away," he said."

The video below covers the details of the Shinkai 6500 submarine used to explore the seabed. (Language is Japanese.)