Since you are not dealing with 3 knot currents and pulling it under to collapse the float, I'd just get the $30 sytrofoam ball 2 piece flag.
But it's the choice of reel that will make it fun or a pain in the rear. I've used the 275ft blue clicker reel below and they work great at $50. But I just upgraded to the Manta Mini reel at $125 and it is sweet. Also get a reef treble dive hook so once you get down on the wreck(etc) you can just hook it off, go explore and come back for it at the end of the dive to ascend
FSD Dive Reel 275ft with stopper
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Thank you for not putting your bare feet in the photo.

Last summer I dived the site in WI that tickets for no flag. Borrowed a flag. It was one of the styrofoam ball ones. Huge and awkward. Buddy did the towing. I definitely do NOT want that one again.