I see from your profile that your in MA. You might be able to collect similar mud along the CT or RI coast, or on Cape Cod. Although on the cape the water in Cape Cod Bay and the Atlantic Ocean is cold, so I'd look to collecting along Nantucket Sound or Pleasant Bay. Also, a lot of the cape is part of the National Seashore, so no collecting there.I’ve bought some mud before from “Florida pets” I think but I’m all honesty, it showed up and I couldn’t see any real life in it.
Also asked a few live rock vendors if they would sell all the rubble/mud/sand they get at the bottom of their vats - that was a no.
would like to find a source that I can access to get shots of life like this.