Russian President Vladimir Putin used a visit to Crimea to join experts on a research submarine in the Black Sea on August 18.
Putin and the experts from the Russian Geographic Society dove to the wreck of a Byzantine ship from the 11th century, which sank near Sevastopol. Putin said it was fascinating.
"This dive should motivate people to get interested in history," he said.
"It's roughly the 10th-11th century, just the time when Russian statehood was taking shape and ties with the Byzantine Empire and other countries were developing. Therefore, I think, this should be interesting both to specialists and the general public and should prompt us all to pay more attention to national history."
It was not the first time the Russian president dove in a small submarine. He made a dive in Lake Baikal in Siberia, the world's deepest lake, in 2009.
Russia's annexation of Crimea in 2014 resulted in an international outcry followed by a series of stepped up sanctions by the West.
Based on reporting by dpa, TASS, and Interfax