Ingredients.
1. Two bullet nose lobster buoys $3-$7 each depending where you buy.
2. Length of PVC pipe 1" diameter $1.50 for 12ft
3. Nylon rope, $7 for 30ft if it's "Rob Allen" or next to nothing if you have old clothes line lying around.
4. Two stainless steel washers 1.5" diameter $1 each west marine.
5. Stainless steel swivel $??
6. Round lead weight that was tapered on both sides. I cut off the tapers to bring it down to 2lb and make it a perfect cylinder $10. I'd mold my own to save on the cutting work.
7. A 1ft length of some kind of hose from Advanced Auto parts that is just perfect for the flag pole $2.
8. Flag and pole.
Tools.
1. Drill.
2. A hole saw to match the diameter of the lead.
3. Drill bit the diameter of the hose.
4. Hacksaw.
I think the pictures speak for themselves. The lead ballast keeps the the flag upright. It also keeps the the buoys from rotating on the pipe. For the flag drill a hole the same diameter of the rubber hose into the widest part of the buoy. Cut the hose so it sticks about 1" above the float and glue in place. The inner diameter is perfect fit for the flag so suction keeps it in there even if the float gets turned upside down with the flag underwater. A stringer can be clipped to the back loop. If more flotation is needed use bigger buoys, different sizes are available.
I put the float in the water and it performed well.