A San Mateo high school water polo and swim coach was arrested Friday after detectives found probable cause to believe that he had engaged in sexual conduct with a student at the school, police said.

Joshua David Tatro, a 25-year-old El Granada resident who had been coaching at Aragon High School for the past year, was booked on one count of sexual assault on a minor and one count of lewd acts with a minor, according to a San Mateo Police Department news release.

Bob Allard, an attorney who is in talks with the victim's family about the possibility of a civil suit against the San Mateo Union High School District, said Tatro started a relationship with the victim in the fall, and it turned sexual.

"It's the same old story of a coach taking advantage of their position and coercing a minor into a relationship," he said.

Allard said his 17-year-old client realized the relationship was wrong and told her mother.

"At some point in time, she realized it was going to a spot where she did not want it do go, and it was a wrong type of situation," he said.

Allard said evidence was collected in the form of emails, text messages and Skype exchanges.

"It was not something she said he did and he denied," he said. "Evidence provided to the San Mateo District Attorney's Office is such that is makes it clear that there was an inappropriate exchange of information with a minor."

Kirk Black, an associate superintendent with the

school district, said the district immediately called police and Child Protective Services when the allegations came to light.

He said there was no need to suspend Tatro because swim season had ended, and he was no longer with the district and would have to reapply next year.

Black said the district is contacting families of other students coached by Tatro but said there is no indication of other victims.

"Obviously, we want to make sure there aren't, but there is no evidence I've heard of that lead police or anyone to believe there was anyone else," he said.

Detectives were able to establish probable cause to arrest Tatro, and he was taken into custody without incident, according to police. Anyone with information on this investigation is asked to call San Mateo police at 650-522-7670.

Contact Eric Kurhi at 408-920-5852.