For UFO enthusiasts, there are few places in Virginia better than Smith Mountain Lake to gather for a conference. Since the lake's inception, there have been numerous accounts from late-night or early morning anglers who reported seeing orbs floating in and out of the lake.

On Saturday, about 30 people, including eight presenters, convened at Mariners Landing Resort and Conference Center for the daylong conference hosted by the Virginia and North Carolina chapters of Mutual UFO Network. Some attendees had their own theories about the lake's orb sightings.

"There are quite a lot of reports of that," said Adrian Olivo, a North Carolina resident who has a background in physics.

Unidentified submerged objects are almost as common as unidentified flying objects, he said. The orbs could be lights on extraterrestrial vessels, seen floating in and out of the water as it attempts to avoid human detection.

Olivo also weighed in on one of the area's most prominent orb sightings, one followed by both UFO and paranormal groups.

In the 1980s, a Huddleston woman reported seeing three orbs flying through her home. The following morning, she found three discolored circles on one of her living room window screens. An analysis of the screen in 2003 found traces of cobalt-60, a radioactive isotope.

"From the description, it sounds like ball lightning," said Olivo.

Robert Swiatek, whose background is in physics and Earth science, touched on this phenomenon during his presentation: "Natural IFOs & Claims of the Skeptics." He said 90 percent of UFO sightings can be explained by five naturally occurring phenomena -- meteors, marsh/swamp gas, ball lightning, earthquake lights and plasma manifestations -- or are hoaxes conjured up by people seeking attention.

UFO enthusiasts, said Swiatek, use science to rule out natural causes for UFO accounts. Ball lightning, one of the more common, usually occurs near thunderstorms or tornados, he said. The balls present in varying sizes and colors, and freely move in any direction. They usually explode and leave behind some evidence of their presence.

"Ball lightning has been said to cause a lot of UFO sightings," said Swiatek. "But if you look at the characteristics, it's easy to rule it out."

But it wasn't the lake's UFO sightings that brought the group together for MUFON's conference. They came for the presentations, which included investigation techniques, Virginia cases and physical evidence from South American cases.

The evening's final session, "The Cape Fear River Case," focused on a North Carolina abduction case from earlier this year. The Discovery Channel interviewed UFO enthusiasts, abductees and witnesses in the case for a program that is set to air in December.

It's one of the 10 percent of cases that has not been explained by natural phenomena or hoaxes. And that, said Swiatek, is what UFO enthusiasts are interested in: the 10 percent.

"When you eliminate scientific facts and explanations," said Olivo, "it must be real."