"It's good to let the community know that it's safe to enjoy the water," Thomas said.
The club was founded by Thomas's sister, Margaux, in 2001 because she wanted to understand what it meant when lifeguards posted warning signs.
Margaux, who is now enrolled in UC Berkeley's business school, earned a scholarship for her efforts with the club.
After a brief decline in club activity after Margaux graduated, brother Marshall took over as president as a freshman in 2004.
Thomas is proud to report there are currently around 30 members monitoring the beaches each week.
"The club is one of the largest on campus," Thomas said.
"Everyone in the club is assigned a beach, and they're responsible for going out to gather a sample each Tuesday, then come into the lab for testing."
Despite the serious theme of the club, activities tend to be more social, Thomas said.
"There are a lot of surfers in the club; not so many are science people," he said.
As members of the club trickle into the lab during their lunch break, they mix their water samples with distilled water and a bacteria-testing chemical before putting it into an incubator.
Twenty-four hours later, Thomas will look at the results.
Club member Max Hilburn, a junior, said he spends an hour a week with club duties.
"It's pretty steady," Hilburn said.
Junior Sanik Patel handles the Crystal Cove testing and was happy to report there have not been any high bacteria levels recorded there.
The most common cause of bacteria pollution, according to Thomas, comes from animal and human feces.
"When it rains, we'll see an increase in bacteria from the runoff," Thomas said.
A couple of years ago, while running a summer program from his garage, Thomas discovered a problem with runoff in Three Arch Bay.
"The city was alerted, and they cleaned the problem up," he said.
Thomas hopes to see his club grow in numbers, and in the summer months he invites the community to participate.
"As long as we have a beach to test there's room for more," Thomas said. 20060106islh0sncDOUGLAS ZIMMERMAN / COASTLINE PILOT(LA)Marshall Thomas, president of Laguna Beach High School's Surfrider Club, tests some water from Table Rock Beach in Laguna for possible pollution.