PUPUKEA — Yesterday morning held the best and the worst for island visitor Elizabeth Dunn. She caught the best wave of her life, then realized her worst fear: shark attack.

Dunn, 28, and her partner, Chris Smith, both of Vancouver, British Columbia, were at Left Overs, a popular surf spot about a mile south of Waimea Bay when she was bitten and released by a shark. It happened so quickly that she's not sure what kind of shark it was, or how big it was.

What she does know is that it left five puncture wounds in her left calf, one to the bone, and doctors said judging by the spacing of the marks, the shark was large.

"I was totally terrified and there was nothing I could do," Dunn said while recuperating at Backpackers Vacation Inn in Pupukea. "It was my worst fear and it's so bizarre to have your worst fear suddenly come true."

Dunn, a psychology professor, has been surfing for two years and said she has a shark phobia.

When the shark hit and released, she knew she wasn't badly injured but couldn't bring herself to put her hands back into the water to paddle in, so she screamed. She was some 400 feet from shore and was sure the shark would return. Instead, it swam away.

Two other surfers were far away and seemed to take forever to hear her, Dunn said, adding that being alone with the perfect wave had its drawbacks.

"It makes you like the crowded Waikiki Beach," she said.

Yesterday's shark encounter was the fourth in Hawai'i this year and the first reported on O'ahu since Feb. 16, 2005, when a shark estimated to be 8 feet long bit a surfer's board near Sunset Beach. That attack happened at 2:30 in the afternoon in clear water about 10 feet deep.

The weather may have been a contributing factor in yesterday's attack. John Naughton, a local biologist with NOAA Fisheries, cautioned yesterday that the runoff from recent rain could bring sharks closer to shore. He said the runoff brings lots of shark food into the nearshore waters and he is urging people not to go swimming there.

In tiger sharks that the fisheries have caught, Naughton said, "we find pigs and goats. One time off Waimea (Kaua'i), we found a horse's head in a shark's belly. People have got to stay out of the turbid water. There's a lot of dead animals in there. Cats, dogs, rats, all kinds. I can guarantee you've got tiger sharks and they're feeding."

Dunn said the surf conditions were perfect before the attack. The water, though murky, was glassy with well-formed waves about 3 feet high. "I was just getting my groove on," she said.

Her last ride was long and euphoric, she said. She turned her 7-foot board to paddle back out.

Then it happened.

The first contact was a bump from below, which she said she thought was a turtle. She'd just seen a turtle and the local man she was surfing with had reassured her that he hadn't seen a shark in those waters in five years. Next, she said, she felt the bite on her left calf before she saw a 2-foot-tall fin, jagged with ridges. The shark released and swam away.

Her rescuers drove her to Kahuku Hospital for treatment.

Dunn's brush with death won't stop her from surfing, but she said she'll be more careful before going in the water. Dunn said from what she can tell, shark attacks are rare.

"The truth is it's so unlikely to happen; it's just that it happened to me," she said.

Reach Eloise Aguiar at eaguiar@honoluluadvertiser.com.