Many people have share many videos of clams moving in water to search for food or to escape from preys, but this video of a razor clam shows movements that are never been captured on camera before and you can also hear some weird noises made by the clam.
There is also a debate going online in which many people claim that it's a Geoduck which is also a kind of saltwater clam. 
As such I am not expert on this topic. You can look at it yourself and make a decision on this.