Two Russian submersibles plumbed the depths of Lake Baikal in eastern Siberia but failed to set a world record on Tuesday for the deepest freshwater dive, expedition organizers said.
"We went down to a depth of 1,580 meters (5,184 feet) and surfed along the bottom for three-and-a-half miles," mission captain and scientist Anatoly Sagalevich was quoted as saying, contradicting earlier claims the dive had gone 100 meters deeper, reported dpa.
The record dive of 1,637 metres was set in Lake Baikal, the world's largest body of freshwater, in the 1990s.
"It was a very flat area without any pits for deeper emersion," Sagalevich said, adding they would "try again."
The dive was the first of 60 planned for the Soviet-designed Mir-1 and Mir-2 mini-submarines to explore Baikal's waters through mid- September.
The mission is headed by pro-Kremlin lawmaker Artur Chilingarov, who led a mission with the same two mini-submarines to plant a Russian flag on the sea bed below the North Pole last August.
The stunt will be repeated on Baikal's sea bed, albeit less sensationally as no country contests Russia's territorial claim there.
The expedition, however, is expected to contribute to global research on global warming and studies of the local ecology are intended to raise awareness of pollution.
Sagalevich projected that the dive could also discover new wildlife as well as new hydrocarbon reserves in what is the world's deepest lake.
Baikal is home to over 2,500 species, and environmental groups fear pollution is threatening the 25 million-year-old body of water.
The lake, which contains more than 20 per cent of the world's freshwater reserves, was declared a UNESCO World Heritage site in 1996. dpa adc mga sc