One of the best places I've found to see wild sea otters up close is the harbour at Moss Landing. It's also one of the best places I've found to get decent fish and chips in California, in the restaurant at Phil's Fish Market. The harbour is in a lagoon behind a spit of sand near the sloughs at the mouth of the Salinas River, where the otters come in to ride out the rough winter seas in the calm of the sheltered harbour.
Here are a couple of otters we saw there on Saturday afternoon.
I'm rather fond of the last of these pictures, where the otter is looking at its most cute. You can find more otter pictures in my Sea Otters photoset on Flickr.