SAN LUIS OBISPO (CN) - Sunday's great white shark attack on California's Central Coast was a textbook assault, said a shark expert who expects more frequent shark and human interactions along the Pacific Coast.
"It's what I would refer to as a typical interaction between a shark and a surfer off our coast in terms of an attack," said Ralph S. Collier, who runs the Shark Research Committee.
As Kevin Swanson paddled on his shortboard along Montana de Oro State Park in Los Osos Sunday morning, a shark surfaced and bit his leg.
"It was really radical," Swanson's friend, New Zealand native Andrew Walsh, told the San Luis Obispo Tribune.
"I was about 10 feet from him, and it was absolutely quiet. ... (The shark) came straight up out of the depths and got him and took him under the water. That was the amazing part: this big giant side of the shark just curving up out of the water."
Despite being attacked by what Walsh described as a 9- or 10-foot shark, Swanson was able to paddle to shore on his own.
Two doctors were walking on the shore and provided assistance. Swanson was airlifted to a hospital in San Luis Obispo and released Monday afternoon.
While it's a common belief that sharks mistake humans for sea lions, Collier said that's not true.
"White sharks have very good vision," he told CNS.
The shark probably knew Swanson was not a sea lion, Collier said, but it most likely didn't recognize the shape.
"This animal came up and was probably investigating the object," he said.
Collier plans to travel to San Luis Obispo County next week to examine the bite marks on Swanson and his board. In the 1970s, Collier developed a system of measuring long-gone sharks by the spacing of the teeth patterns they left behind.
If this one was 9 or 10 feet, as Walsh said, it would be a "sub-adult." Juvenile great whites are shorter than 9 feet, Collier said, while adults are 14 feet and over.
There have been just two recorded fatal shark attacks in San Luis Obispo County - one killing a Cal Poly student frolicking in the waters of Morro Bay in 1957 and another that claimed the life of swimmer Deborah Franzman in Avila Beach in 2003.
Two other Central Coast men - a surfer and a boogie boarder - were killed 40 miles south of the county line, in Northern Santa Barbara County, in 2010 and 2012.
Because there are more protections for great whites, Collier said, their numbers are growing. And since there are greater populations of pinnipeds near the shore, sharks are more likely to gravitate there for food.
And more humans are entering the water for recreation, making shark-human interactions more likely.
Roughly 50 percent of shark attacks in the Pacific Ocean occur from August to October, Collier said, when the ocean water is warmer. Yet, predicting great white behavior is nearly impossible.
They are mobile creatures, he said, and it's unclear if they breed in a particular area.
"There isn't a specific place where we can say it's safe," he said.
Collier said that buying shark repellent is likely a waste of money.
"There is no 100 percent deterrent on the market today," he said.
A surfer's best defense, he said, is to be alert in the water. Signs of sea lions and bait fish fleeing in a hurry might suggest a good time to end a surf session.
"If there's a shark sighting in an area, I'd avoid it for about a day," he said.
There have been just over 100 shark attacks on humans in the state since the 1920s, including 13 fatal attacks, according to the California Department of Fish & Wildlife. More than 80 percent of the attacks have been north of Point Conception, which is in Santa Barbara County.
While Swanson's attack garnered international attention, the well-known surfer was back home in Morro Bay Monday, responding to the many comments friends had left on Facebook.
He wrote to one friend: "Only one choice and that is to paddle your ass off for shore, and hope there are some amazing people close by."
Read the Top 8
Sign up for the Top 8, a roundup of the day's top stories delivered directly to your inbox Monday through Friday.