The best buoy for freediving and spearfishing

What's good about this buoy

High visibility
A good buoy should be easy for boats to spot.
Mesh bottom
A mesh bottom lets the water drain out of your buoy, making it much easier to lift out of the ocean.
Easy to inflate and deflate
Older buoys contain a car tire inner tube, which you could (very slowly) deflate by hand but had to inflate at a gas station. Newer buoys have a quick-release deflation valve and can be inflated by mouth. This newer style makes your buoy easier to transport in a car trunk or on a plane.

No mesh bottom
A buoy with a solid bottom won't drain, making it super heavy when you exit the water.
Low quality zippers
Look for buoys with YKK zippers or similar. Low quality zippers will break and/or oxidize shut over time.
Car inner tube
Not a dealbreaker, but if your buoy contains a car inner tube rather than being inflatable by mouth, it will take up more space in your trunk and be harder to travel with. On the other hand, the extra buoyancy provided by a car inner tube can be a plus if you are doing deeper (30-60m) free immersion dives. For dives less than 30m it doesn't matter.