And sure, those options could include your waterproof and crack-resistant smartphone, but keep in mind that the best action camera is designed for this kind of shooting. Plus, just because your phone is tougher, it doesn't mean you should risk losing or damaging the thing that keeps you connected to work, family and friends. It's also way easier to mount one of these to your body, car, bike or anything else than your phone.
Are Gopros waterproof?
Although obvious, I put this here first because this is one of the most important factors when purchasing your camera. The HERO3 has three editions (white, silver and black), ranging from $199 - $399 (prices continue to drop annually as newer versions are released -- we'll keep you updated on those). The HERO2's are at the bottom of this gap, but aren't as "new" and lack some features the 3's have (they're discontinued at this point but can be found on the net here and there).
GoPro cameras are known for their premium shooting capabilities, but not all of them hold up underwater. Some options are a bit blurry, while others lack great depth. Always ensure the GoPro you take diving is able to shoot as well underwater as it can on land. A bit of quality difference is not the end of the world, but you want your videos to be as clear as possible.