Divers swim near the Zenobia shipwreck, a Swedish built ferry that capsized and sank off the coast of the Cypriot port city of Larnaca in 1979 during a 'Mass Dive' event in which over 120 divers participated, on June 28, 2015. [Emily Erving-Swift/AFP]

An iron and steel colossus that sank on a summer's night 35 years ago off Cyprus is now considered one of the world's best shipwreck dives.

Thousands dive down each year to see the Zenobia-the "Titanic of the Mediterranean"－which is slumped on its port side at a depth of 40 metres (130 feet) off the island.

The roll-on, roll-off Swedish ferry, named after a third-century queen of ancient Palmyra, is the top wreck dive in Europe, competing with sites in the Red Sea, Asia and off Australia.

"It's so big you can dive a few days and not get bored," said Mat Howell, who works for a British-based scuba diving holiday firm and was in Cyprus for the annual "Zenobia Week" at the end of June to promote the site.

Unlike many other wrecks, the Zenobia is easily accessible, only a 10-minute boat ride from the coastal resort of Larnaca.

Like the Titanic which sank in the Atlantic in 1912, the Zenobia came to grief on its maiden journey on its way to the Syrian port of Tartus.

On June 2, 1980, shortly after midnight, the captain of the listing vessel sent out an SOS.

Trawlers went to the rescue from Cyprus but to no avail and the Zenobia went down five days later, without loss of life but with around 100 articulated lorries loaded with cigarettes, cables and one million eggs still on board.

Theories for the cause of the disaster range from navigation errors, ballast problems and an insurance scam to sabotage because of an alleged secret consignment of arms.