An Oregon State University oceanographer piloting a one-man submarine has become the first person to see the bottom of Crater Lake, the nation's deepest lake.

Jack Dymond explored the south-central area of the lake at a depth of about 1,450 feet in search of hydrothermal vents, or hot springs, during an eight-hour dive Friday in the one-man submersible Deep Rover.The deepest point in the lake is 1,932 feet, making it the seventh-deepest lake in the world.

Dymond's dive, conducted a day earlier than planned, was part of a three-week exploration of Crater Lake, which is funded by a $225,000 grant from the National Park Service.

"It was very rough terrain down there," said Jim Milestone, natural resource management specialist for the National Park Service at Crater Lake.

Crater Lake was formed nearly 6,900 years ago when a volcano, Mount Mazama, erupted violently and exhausted its supply of magma or molten rock, and then collapsed into the empty magma chamber.

Milestone said Dymond explored a rugged fault, part of a fracture line that rings the floor of the lake.

Dymond and colleague Bob Collier, both oceanography professors at Oregon State University, theorize that hydrothermal vents exist along the fracture line, feeding the lake with hot water, chemicals and sediments from a source underground.

Results of Friday's dive would not be released until Sunday, the researchers said.

Milestone said Dymond and Collier decided to take the first deep dive Friday because they felt comfortable with the submersible after taking shallow two-hour dives Thursday.

Collier was to take his turn on the lake floor Saturday, Milestone said.

The rough lake floor made it difficult for navigation equipment to keep track of the 10-foot-long craft, Milestone said.

The dives are being recorded by cameras mounted on the submersible, which also has maneuverable, pincerlike arms and instruments to measure temperatures and other data.