Mike, that one of mine I made out of an old folding tent pole, a fishing float and a big sinker to keep it upright that I found on the bottom of Shark River.
I went with that design because it’s just buoyant enough to float but when swimming under docks or mooring lines I can pull it under. The folding part comes in handy when I go down to Blue Heron Bridge.
I think I have more of the tent pole if you want it. I also saw one made using one of those reflective fibreglass driveway markers.