Submarines hunt for fuel in Russia's Lake Baikal
3 August 2010 Last updated at 11:00 BST
Russia may have some of the largest oil and gas reserves in the world, but the hunt for new deposits to replace exhausted fields is underway.
In East Siberia, submarines are searching for gas hydrates, a potential alternative fuel source, deep down on the bed of Lake Baikal.
The BBC's Katia Moskvitch watched them take a dive in the world's deepest lake.