Go see Dave over at the Ship's Store at Fay's. I was in there a couple days ago and he had some floats with flag sticks that are easily over 3 feet tall and he has dive flags in stock.
Besides DW and Fathom's you have Aquanuts Scuba in Concord as well on Manchester St at Airport Rd.
Pot hunting? Do I have to take a safety course before I hunt for them? And wear an orange hat or wetsuit so others searching for the elusive bean crock pot don't accidentaly speargun me whilst searching the bottom for rubbish? What's the limit a day?
Speaking of pot....off of a local swimming beach a few years ago I found a very nicely made hand blown pot pipe. Exquisite colors and all. Turned it in the cops but at last check no one had come in to claim it....wonder why....
A lot of neat pottery shards laying around in the miscellaneous stuff off the Messer Street boat ramp for those interested in a shallow dive/snorkel....it's a nice and toasty 43 there right now so you'll need at least a 3mm shorty...lol