Extension works well: extends as it should and holds the GoPro perfectly. Unfortunately, the shaft fills up with water after the first use. The water in the inner (expanding) section got stuck, but I was able to "pump" the water out of the outer section, but I couldn't figure out how to pump the water out of the inner section. I added a floating bracelet in addition to the sealed handle to help with swimming. I didn't understand if it still floats when it's completely filled with water, but if you pull it out in the water, the water will definitely get to the outer part.