curious on equipment

I use a garret sea hunter mark II, I've tried wading and scuba with it while using tools and no tools. If you are wading, I would recommend getting a good solid sand scoop, there are a lot of choices on that. For staying on the beach, I went to the dollar store and got some cheap colanders to sift through the sand, the plastic ones allow you to scan while sifting with no interference. Sand scoop would be around $100-150 for a good one, dollar store colander around $2.

You are going to hear the At-Pro will not work in wet sand or the surf. Everything I have read points to the same.

HOWEVER, some say they can find things. If dry sand all you really need is a scoop from feed and seed and drill holes in it. If going in the surf, you need a long handled scoop. Read the thread on scoops above.

You would also need a wet suit and booties or waders in cold water. Also depending on your experience and or comfort a PFD.

I've read you can manually ground balance an ATP to around 9 or 10, and knock the sensitivity down from wide open and one can manage alright in the salt water... A little chattery but if you know what to listen for...

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Yeah, you gotta have an expensive detectorists scoop, or a reasonable facsimily thereof....Also, wear shorts and a short sleeve hawaiian inspired button up... go barefoot or sporting Crocs or Clarkes sandals...black polyester argyle socks pulled up to your knees too...trust me, Nobody will mistake you for a clam digging poacher!
Mud

You can use a ATP around salt water but not without noise problems. A good sand scoop with a long handle is the ticket.

I've hunted the sandy WA and OR beaches with my ATP. A sandscoop is highly recommended. A cheap one if you stick to the dry sand or a more robust one when the sand is wet or if you're in the gravel/rocks. I can't say I've found much down in the wet sand along the water, but up in the dry sand where people have made fires and whatnot I've found a good amount of change and beach toys. However, there is usually a lot of trash and iron contamination from junk and nails that get thrown int the fires. Be prepared for aluminum nuggets (melted aluminum cans), nails, and foil.
I've been primarily disappointed with my beach finds, but it's still fun to get out and try…and you never know what might turn up. The ATP does well in the dry stuff and can do OK down by the water, but you do have to GB regularly and drop the sensitivity to get rid of the chatter.