Do a web search for "Atlantis" and you'll find a lot of dubious claims about this legendary island civilization. The story of Atlantis, as most people know it, comes from the writings of the Greek philosopher Plato. According to his writings, Atlantis existed about 9,000 years before Plato himself wrote. The people of Atlantis were an advanced and prosperous civilization who grew too arrogant and were eventually destroyed by the gods. He describes their island city in some detail, describing a sophisticated canal system and multi-story buildings with indoor plumbing. The story of Atlantis was supposedly brought to Greece by another philosopher named Solon, who learned it in Egypt.
Assorted psychics and other supernaturalists have tried to attach themselves to the Atlantis legend, including Ramtha-channeler JZ Knight. They've made wild claims about the achievements of the Atlantean civilization and claimed to have located the city everywhere from the Indian Ocean to shallows of the Carribean Sea. Some have even postulated an entire continent in the middle of the Atlantic Ocean, now sunk beneath the waves. Needless to say, none of their expeditions to these places have turned up anything substantial.
You'd think with all the woo surrounding the story of Atlantis that scientists would want nothing to do with it, but scientists actually studied this story fairly seriously. They've looked for an ancient civilization that fits Plato's description and predates him, preferably located where its tragic tale might have found its way to Greece. Their search resulted the History Channel program called Lost Worlds: Atlantis, which I found myself watching a few nights ago.
Modern scientists have traced "Atlantis" to the Santorini island group which lies north of Crete. Crete itself contains ruins of the Minoan civilization, which was far more advanced than any of its Mediterranean contemporaries, at least in the field of architecture. The Minoans built a multi-story palace at Knossos on the northern coast of Crete that included earthquake-resistant reinforcements and indoor plumbing. They seem to have accomplished many of the "wonders" that Plato describes in his tale of the doomed city. The Minoan civilization fell at about the time of the Thera eruption in 1500-1600 BCE.
Thera is one of the islands in the Santorini group, but it was not the center of the eruption. Thera is just one of several islands that form a ring-shape in the Aegean sea. All of these islands, save one, are part of the rim of a volcano. The central island, Nea Kamini, is the top of the caldera of the volcano. Nea Kamini is a young island that has formed since the Thera eruption. It's quite likely, however, that a similar island existed before the Thera eruption. If "Atlantis" was on this volcanic island, then it truly would have been obliterated in the Thera eruption, since that island would have been the center of the largest volcanic explosion in human history.
Modern archaeologists did not rely on channelling the spirits of dead Atlantean citizens to locate the lost city. They did the hard work of digging out artifacts, dating them, tracing their origins, fact checking against Egyptian records, identifying new sites, digging more, and analyzing their finds to determine that the Minoans had colonized the Santorini islands in the second millenium BCE. They dug through thirty feet and more of volcanic ash and pumice to find the ruins of a Minoan city on Thera. Real science has done more to determine what truth might lie behind Plato's tale of Atlantis than any channeler, dowser, or other psychic has ever done.
If the full truth of the tale of Atlantis is ever going to be found, it's going to be found by scientists, not psychics.