Welcome aboard! Great suggestions by all.
You may want to investigate the XP Deus metal detector. It’s super light weight and won’t mess with your bad back. It also has, as an extra, a waterproof kit so you would be able to hunt the water. I use mine primarily at the beach.
Good luck!
Do consider a long handle scoop for the dry sand as well as the wet sand or you will be bending up and down. Stainless steel is the way to go. I’ve used mine as a shovel and just to do a quick grab for surface items. The hand wire basket types sometimes will allow smaller items to pass through.
I’ve owned both types and the hex holes are my preference after hundreds of hours of sifting sand both wet and dry. Best of luck out there!
I agree that Simon would be the guy to talk to. I’ve never used a pin pointer at the beach in the last 7 years. A quality scoop like a Sito? (I believe they are Australian) may be just the ticket. Too small of a scoop does not get the job done. Good luck!