Hey NADO. I have been shooting with GoPros for 3 years now, from the Hero 1- 3. I have not used the 4, and each of the products seems to have a few new features and pros and cons. but here are a few thoughts anyhow...
I shoot in 1080p 30fps and one battery usually covers a day of fishing, (although the Hero Black edition burns battery power much faster than others.) I usually run the camera for the first 5 minutes at a spot, and then shut it down until something actually happens. But if you have 2 batteries you should be fine for 6+hours.
I like this method of filming (as opposed to continuous filming) as it is easier to sort out which clips (files) are what. It also makes you check the lens more often (a few water drops can ruin the prime clip or moment). sometimes running the camera's continuously results in a fog / condensation building in the case due to the heat of the battery. the vented backdoor helps too, just don't dunk it.
I guess the only other tip is that I like to shoot from a stationary or fixed position.. the image quality is so much better, and you can do more with it on the editing side. so I have mine on a small monopod (just a broken leg of a tripod) and have modified it to have a spike (tentpeg) on the bottom. That way I can roll into a spot and stick the camera down in the mud (or snow)and start fishing and get good angles and the whole shot.
have fun, filming has become my second favourite hobby next to fishing