Deep search: Tech-enabled discoveries of underwater treasures

The Antikythera shipwreck (c 60 BCE): Greek sponge divers first stumbled upon the wreck in 1900, and marvellous statues and works of art were recovered. Among these is what is considered the world’s oldest analog computer, the Antikythera mechanism. The ancient Greek mechanical device relied on astronomy and mathematics to track the position of planets with respect to the sun and to predict eclipses.

In 2012, new dives were conducted using closed-circuit re-breathers (that let divers stay deep undersea for longer), high-resolution cameras and diver propulsion vehicles, which documented a second wreck at the site. In 2014, special exo-suits allowed divers to descend over 1,000 ft and stay for hours. Last month, researchers also used a balloon system created by the Swiss watchmaker Hublot, to lift underwater boulders out of the way. On these expeditions (part of an extended, ongoing programme by the Swiss School of Archaeology in Greece, University of Geneva, and the Greek government), divers have recovered anchors, spikes, ceramic bowls and a marble head believed to be from a 2,000-year-old statue of Hercules. In the next phase, Hublot is set to design robots by 2023 that will replace human divers, stay underwater longer, and relay data and analytics back to shore in real time.

Pavlopetri (c 3000 BCE): Discovered and first mapped in the 1960s, this site lies off the coast of southern Greece and is considered the world’s oldest submerged city. It consists of ruins of homes and other structures, clearly marked courtyards and streets, graves and rock-cut tombs. In 2009, the Pavlopetri Underwater Archaeology Project (an initiative of University of Nottingham and the Greek ministry of culture) used a robotic total station that logged the position of the artefacts with high accuracy and sector-scan sonar mapping that surveyed the submerged town and created a digital reconstruction of the structural ruins within it. Using CGI they built a digital approximation of the 5,000 year old city, with two-storey houses, walled courtyards, well-defined streets and a cemetery outside the city. Scattered all over the site, submerged in the seabed were hundreds of pithoi, or large storage vessels which suggests that Pavlopetri was a centre for commerce.

Dwarka: The search for the legendary sunken city mentioned in the epic Mahabharata began in 1981 and continued for two decades, during which over 500 artefacts were recovered off the coast of Gujarat. In 2007, underwater archaeologist Alok Tripathi led a detailed excavation by the Underwater Archaeology Wing (UAW) of the Archaeological Survey of India (ASI). The team used multi-beam echo-sounders to map the seabed and divers found stone structures such as pillars and anchors that established it as an ancient port. After being non-operational for almost a decade, UAW hopes to begin explorations again. “India has vast unexplored seas that need to be surveyed and studied. We need to revive the underwater archaeology wing and train more people in this division,” Tripathi says.