It is worth noting that you can operate an action camera underwater, granted you abide by its waterproof rating. But, it is not possible (unless you have a cable that can carry the signal) to utilize the Wi-Fi technology in action cameras underwater. The reason for this has nothing to do with action camera themselves, but with the limitations of Wi-Fi. As GoPro points out, as soon as your device is underwater, any connection that is using Wi-Fi will be lost.
Wi-Fi waves simply do not work well underwater and as they have no tolerance towards them, it is practically impossible to do so. Maybe someday computer engineers and devoted technology enthusiasts can figure out a way to leap this hurdle, without the use of a cable. For now, though, forget trying to transfer your photos to your smartphone while you are submerged in water.