It looks like promotional photos and/or a commercial were being shot of a Power Wagon in Humboldt County, near Moonstone Beach, when things went awry. According to reports, the truck got stuck on a rock, and when the tide came in, the Power Wagon ended up in the water. The photo crew called a local towing company, which pulled the Power Wagon back onto dry land. In the links below, you can look at still shots of the truck in the ocean, and of the recovery efforts. One person also filmed a video of the recovery.
Source: Lost Coast Outpost, McKinleyville Press