Instead of looking for the clam "shows" in dry sand, I prefer to broadcast rake in the water. My reason for this is that not all clams will show, so you will be walking over clams looking for the ones that are showing, and less people work in the water. Only people that are somewhat serious about clamming work the water, especially deeper. I raked in the shallow water there for the purpose of making the video, but if you wade in to 3ft+ of water you can find a lot more big clams.
The vast majority of people that clam Netarts are fairly inexperienced and almost always gravitate towards to middle of the big tidal flat or stay close to the parking areas. This means that even the very best areas are relatively untouched, just because a lot of people are inexperienced. There is a guy that comes out in a boat every time I'm there (he lives there and I only go on the best tides, probably why), and he is somewhat of a professional at clamming. When he goes for cockles he almost always rakes the sand in the water or goes way out on the tip of the flat and looks for shows in dry sand where almost nobody else goes.
That being said, if you are in a cockle bed you will find them in both dry sand and in the water. It's just better quality clams where people can't as easily get to them.