Any kind will work on the flats so long as it is appropriately sized for the boat. The flats don't usually have a lot of current or tidal flow so anchors aren't very critical and you don't have to worry about losing them. Now the river is an entirely different matter-there I use a hunk of steel that someone hid in the bottom of a bucket of sinkers my father-in-law bought at an auction. It's not uncommon to lose an anchor in the river.
i had been useing a mushroom anchor but when waters moveing good it seemed to skip or drag along and not bite. i went back to danforth and lt works better for me.that said i would agree with jerry pc of old steel or a coffee can filled with concrete[homemade anchor] up river.with dam release water supposedly comes fast and may need to cut anchor line. hope that helps