KIHEI, Maui — As a former triathlete, Jonathan Genant of San Diego often takes long ocean swims when vacationing on Maui. But yesterday's workout off Keawakapu Beach was violently interrupted when a shark emerged from the deep to attack him about 200 yards from shore.

Genant, 29, lost a portion of his left hand, including his pinkie finger and the tip of his ring finger. He underwent surgery at Maui Memorial Medical Center and was expected to be released today.

Some of South Maui's most popular beaches, packed with holiday vacationers and local children fresh out of school, were closed in the aftermath of the shark attack. The coastline from Polo Beach in Wailea to Kama'ole Beach Park 3 in Kihei was expected to remain closed until noon today.

It is not known for certain what kind of shark bit Genant, but a Maui Fire Department helicopter spotted a 10- to 12-foot tiger shark close by shortly after the attack. Tigers are responsible for the majority of shark attacks in Hawai'i.

Three previous incidents of sharks biting surfboards and a kayak off Maui were reported this year, but no one was hurt, according to the Department of Land and Natural Resources. The last fatal shark attack in Hawai'i occurred April 7, 2004, when surfer Willis McInnis, 57, was killed by a tiger shark in murky water off Kahana in West Maui.

Genant's father, Harry Genant, said the family is grateful his son wasn't more seriously hurt.

"It could have been so much worse," he said.

Jonathan Genant was swimming alone in calm, clear waters about 11:30 a.m. when he saw the shark come up from under him, his father said.

"It was huge and its jaws were wide open. He knew it was going to take a part of him," Harry Genant said. "It chomped on his left hand and he heard a snap and could see that his digit was missing.

"It was pretty terrifying."

The San Diego man used his right hand to clamp down on the wound to control the bleeding, then turned over on his back and began kicking toward shore, all the while worried the shark would return for the kill.

When Genant was within about 100 yards of shore, beachgoers were able to hear his cries for help.

Brock Smeaton of Vancouver, British Columbia, who was at the beach with his family, said he heard the man calling out and saw Genant holding his bloody hand above the water.

Smeaton said about eight or nine people entered the ocean to assist Genant, who was brought to shore on a body board. Firefighters from the Wailea Fire Station provided first aid until the injured man could be taken to the hospital.

His parents were at their Wailea condominium when they got word of the shark attack.

Throughout much of the afternoon, two DLNR watercraft patrolled the nearshore waters, assisted by a county water safety officer on a rescue craft. A Maui Fire Department helicopter scanned the ocean from above, looking for predators.

On shore, DLNR enforcement officers walked up and down the beach to keep people out of the water.

Smeaton and his family were among those reluctant to leave the 2- to 3-foot shorebreak. He said the shark attack wasn't going to spoil his family's vacation. "You can get hit by lightning just as easy," Smeaton said. "I'd be back in the water if I could be."

Jonathan Genant, who co-founded an Internet marketing firm called Better Deal LLC, visits Maui annually with his parents, Harry and Gail Genant, and other family members.

His parents are physicians in San Francisco. Jonathan arrived on Maui a day before the shark attack.

Harry Genant said Jonathan has been swimming most of his life, and although he no longer competes in triathlons, he remains active and regularly trains with 2- to 3-mile ocean swims. He said his son favors calmer waters farther from shore and away from reefs.

Swimming alone and far from shore are two things to avoid in order to reduce your chances of a shark attack, said Russell Sparks of the DLNR's Division of Aquatic Resources.

Other tips include staying out of the water at dawn and dusk, and avoiding murky water and stream mouths.

An average of three to four shark attacks occur annually in Hawai'i.

The earlier Maui incidents occurred Oct. 13, when a shark bit a surfboard about 100 yards off Honokowai; May 14, when a shark grabbed a kayak about a half-mile off North Kihei; and May 2, when a shark gnawed on a surfboard about 70 yards off Ku'au.

On Feb. 16, at Sunset Beach on O'ahu's North Shore, a shark bit a surfer's board.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.