Review on Polyform A-Series Marine Buoy by Bradley Stewart

I had to buy this because it's the exact model used in a robotics competition. There is an threaded hole for inflation at the bottom that comes with a white, plastic cap for sealing it. The cap isn't very effective at keeping water out: after a few dozen hours in the pool, the buoy was about 1/4 full of water. Also, if you lose it, the water pressure will cause the buoy to collapse.