GoPro video cameras are fantastic for underwater shooting, but they have one fatal flaw: they sink like a stone. YouTube channel Wandering Designers shows how to turn a standard bottle cap into a cheap float for GoPro, to be used with any drinks bottle.
There are third-party floats for the GoPro, but they cost a lot and it's just additional equipment to carry with you. Instead, the video above shows how you can make a GoPro floating mount for cheap. You'll need a standard GoPro tripod mount, 3mm bolt and nuts, a pack of Sugru (or the free DIY Oogoo), 3mm rubber washer and a Coke bottle cap.
As the video shows, you need to drill a hole through the cap and push the bolt up through the bottom. Apply Sugru to make a watertight seal, and put the rubber washed on top and screw on the tripod mount. And that's your portable DIY GoPro float.
Attach this mount to any empty drinks bottle (they're standard size across the world) and your GoPro will float right below the surface of the water -- no more worries about losing your grip and seeing that expensive camera sink to the floor. Plus, you can also do some hands-free shooting this way!
How to make a GoPro float with a Coke bottle & Sugru [Wandering Designers via Sugru blog]