OK, I've spent most of my life fishing on the ocean off the lower 48. I was a crab fisherman for many years and can tell you that crab like to come in close to shore the calmer the ocean gets to feed on their favorite, razor clams. I did not like fishing crab in close to the surf, but I know others that did. When a storm comes in those pots that are in close may get sanded in due to the turbulence and the bait jars will fill with sand. In front of gold bearing rivers, and on either side, pots have been recovered by those I know after being sanded in and the bait jars will be full of black sand. Sadly, I've never collected any of the black sand or had my friends save me some. Maybe the mouths of these rivers could be prospected looking for black sand on the low minus tides. Maybe use a clam gun (suction tube) to get down deeper looking for the layer? Maybe I'm crazy, but I know the fine heavies are there.