The team will search for sunken remains of the armada - sent by the Achaemenid Emperor the King of Kings Darius the Great to invade Greece - which was annihilated before reaching its target.

Waters off Mount Athos in northern Greece, the site of the disaster, have yielded two helmets and a spear-butt. Experts will return to the site in June to look for more remains of the fleet.

"This is an extraordinarily target-rich area for ancient shipwrecks," Dr Robert Hohlfelder, a maritime archaeologist at the University of Colorado, Boulder, US, told BBC News Online. "Usually, when shipwrecks are found, the archaeologists are asked to create the history around them. We have the history, now we've got to find the shipwrecks."

Historical Cue
An account of the 492 BC disaster is related in The Histories, by the 5th Century BC Greek writer Herodotus. He says the ships were smashed against Mount Athos.

Last year, the team discovered a shipwreck containing amphoras, pottery containers used for transporting foodstuffs. How, if at all, this wreck relates to the disaster is not known.

The archaeologists also found a bronze spear-butt, called a sauroter, at a site where, in 1999, local fisherman raised two Greek classical helmets from the seafloor. The sauroter was found in the possession of an octopus, which had dragged the spear-butt inside a jar in which it had made its sea-floor home.

The survey could help resolve arguments about how triremes - ancient galley warships used by the Persians and Greeks - were constructed.

Recycled boats
In trireme battles, victory hinged on slamming other ships with a heavy bronze ram on the front of the ship. Not a single trireme wreck has ever been found and archaeologists on the survey are divided over the likelihood of finding one on this expedition.

"We will not find a trireme. They contained very little ballast so they floated. Although the rams may have sunk," team member Michael Wedde told BBC News Online. Classical texts refer to triremes being rescued, towed to dry land and repaired to be reused.

"There's some question over whether they sank," said Dr Shelley Wachsmann of Texas A&M University in College Station, US. "Most ships we find have cargoes because those bring them to the bottom,"

But Dr Hohlfelder said there was a possibility a trireme could have sunk to the sea bed: "Underwater archaeologists have wish lists. A trireme is certainly one of the top ones on most people's lists. And I think this is one of the best places to look for them."

It is also possible that supply ships - which supported the warships - were carried to the bottom, weighed down by their cargoes. The project is a collaboration between the Canadian Institute of Archaeology and the Greek Archaeological Service.

Katerina Dellaporta, of the Ephorate of Underwater Antiquities in Greece, and Dr Wachsmann are leading the research. Around 20,000 men were lost in the disaster, which shook Persia at a time when it had its sights on assimilating mainland Greece within its empire.