Robert Sarmast said a Mediterranean basin was flooded in a deluge around 9000 BCE which submerged a rectangular land mass he believes was Atlantis, lying 1.5km beneath sea level between Cyprus and Syria.
"We have definitely found it," said Sarmast, who led a team of explorers 80km off the south-east coast of Cyprus earlier this month, on Sunday.
Deep water sonar scanning had indicated man-made structures on a submerged hill, including a 3km-long wall, a walled hill summit and deep trenches, he said. But further explorations were needed, he said.
"We cannot yet provide tangible proof in the form of bricks and mortar as the artefacts are still buried under several metres of sediment, but the circumstantial and other evidence is irrefutable," he said.
At a news conference in the port city of Limassol, Sarmast provided only animated simulations of the hill.
"We cannot yet provide tangible proof in the form of bricks and mortar as the artefacts are still buried under several metres of sediment, but the circumstantial and other evidence is irrefutable"
Whether and where Atlantis existed has captured imaginations for centuries.
According to ancient Greek philosopher Plato, Atlantis was an island nation where an advanced civilisation developed some 11,500 years ago.
Theories abound as to why it disappeared, from Atlantis being hit by a cataclysmic natural disaster to the Greek myth that says the civilisation was so corrupt, greedy and power-hungry it was destroyed by God.
Sceptics believe Atlantis was a figment of Plato's imagination.
Sarmast says he was led to Cyprus by clues in Plato's dialogues. Plato's reference to Atlantis lying opposite the Pillars of Hercules - believed to be the Straits of Gibraltar - have often led explorers to focus on either the Atlantic Ocean, Ireland or the Azores off Portugal.
"People who dismiss this have not really done their homework; sceptics don't really understand," said Sarmast.
"To understand the enigma of Atlantis, you have to have good knowledge of ancient history, Biblical references, the Sumerian culture and their tablets."