San Marcos swim remained undefeated in dual meet action with a Channel League sweep of Rio Mesa on Wednesday in Oxnard. The Royals’ girls team came out on top by a score of 121-39, while the boys squad earned a 94-38 victory. San Marcos will look to complete the undefeated season when it hosts Camarillo for Senior Day on Thursday at 2:20 p.m. Kate Crowder was the lone double individual event winner for the San Marcos girls, emerging victorious i…