Rent a kayak at Van Damm and go south to the heritage house . There is a protected area there behind some small islands, the waves break there oxygenating the palm kelp and the abs hang out there to feed. In any area the bigger ones are down about 30 feet.
There are also some good spots outside of the Navarro State beach. The mouth of the river silts in during the summer so you'll have to walk out to the surf a ways.
Abs have increased since the urchin industry has made space for them. 10 years ago they would huddle in little groups unable to move around because the urchins were EVERYWHERE. they ate so much kelp that the abs had a hard time finding food.