SAN DIEGO -- A woman making her second dive of the day into a sunken ship off Mission Beach was rescued Saturday after she came to the surface unconscious, a lifeguard lieutenant said.

The woman was exploring the the former Canadian destroyer Yukon when she "had some difficulties and made a rapid ascent," Lt. Nick Lerma said. "When she surfaced, she was unconscious."

Her instructor and the crew of the charter diving boat Marissa pulled the woman from the water and rendered first aid, and called lifeguards around 11:20 a.m., Lerma said.

She was able to walk off the rescue boat when she returned to shore, the lieutenant said. She was taken to UCSD Medical Center.

Lerma stressed that the victim survived because she was with a partner when she dove, and he praised her instructor and the crew of the Marissa, which is based at Seaforth Landing on Mission Bay.

The Yukon was flooded and submerged 1.8 miles off Mission Beach in 2000 to to create a diving reef. It sits in 40 feet of water and has become a famous dive spot.