Sandworms (genus Nephtys) live in the mid-intertidal to deep-sea area. We found this worm while digging for littleneck clams at the edge of the Hama Hama delta. They are nocturnal predators, and use the proboscis to capture their prey: small worms, molluscs and crustaceans. They also evert the proboscis to create tunnels through the sand. Probably that's what this worm was attempting to do... he wasn't trying to eat a human hand; he just wanted to get out of the spotlight. For a more detailed description of nephtys anatomy, go here.
Some marine worms have venomous glands at the base of their jaws that secrete a neurotoxin. Fortunately for the camera woman, this worm isn't one of them.