MARTINEZ -- A former swim and water polo coach pleaded not guilty Monday to felony charges alleging sex crimes against a teenage girl, according to the Contra Costa District Attorney's Office.

Christopher Yang, 27, of Walnut Creek, was charged in April with nine felonies, including four counts of unlawful sex with a minor. Yang has coached at Northgate High School in Walnut Creek and Campolindo High School in Moraga, but authorities are not saying how he knows the girl.

"This is a regrettable situation for everyone involved, and Mr. Yang accepts responsibility for his lapse in judgment in his brief relationship with the alleged victim," Yang's attorney, Marvin Lew, said.

Yang remains out of jail custody on $610,000 bail. He returns to court June 18 to schedule his preliminary hearing.

Contact Malaika Fraley at 925-234-1684. Follow her at Twitter.com/malaikafraley.