Water quality unsafe in Santa Cruz?

Hi, I am from San Diego. I am going to be living in santa cruz for about a year. I thought the water quality would be very clean, but to my dismay, I found that cowell's beach is ranked one of the worst beaches in california.
Could someone tell me how the water quality fairs throughout the year? I read that in the summer there are "no swimming" signs because it gets very bad.
Could someone tell me how the water quality fairs throughout the year? I read that in the summer there are "no swimming" signs because it gets very bad.