I've used a GoPro for years. Pros:
- Easy to use
- Waterproof
- Video Quality is good
- GoPro's own software is fine for editing this type of footage
Cons:
- It's a POV camera... fisheye, eventually boring perspective over time, etc.
- Chesty chest mount is a pain for fishing
- Mounting on head / hat is heavy
- I'm not sure many people realize it, but all those really great GoPro "professional" videos have had a lot done to them in post production to handle shake, fisheye, etc.
I use mine mostly for other things these days. Instead I bought a small, good waterproof camera (mine's the Nikon, but there are others that are good as well). It's HD video has no fisheye/distortion and is great quality. It also takes great still photos. It's nearly as light and is waterproof. It doesn't have all the "on body" mounts available.
I can vouch for the Peak Designs Capture clip mount that was mentioned. I've used it with the GoPro, point and shoot still camera (the Nikon), DLSR cameras... It's a great accessory. If you're using it with a light camera like a GoPro or small point and shoot, you only need the lesser expensive Capture. The more expensive one is intended for heavy DLSR cameras. As someone else noted, you can attach the Capture to anything that's "strap-like" so a belt, wader suspender, chest pack or backpack strap, etc. The camera can be disconnected quickly. So what I do is also carry in my pack a little tripod. So if I want to, I can pop the camera off the mount and quickly put it on a little tripod. If I'm in "filming mood" I can do that and capture different perspectives than just POV to edit together.
If I were to buy another GoPro for fishing, I'd go with the cheapest one they have in the line-up now unless you're buying it for 4K video and specialized video production. For fishing, anything other than the least expensive one is overkill in my opinion and while it's waterproof and rugged, you drop it in a deep spot and you're screwed. Having done exactly that once, to anyone who is fishing with a GoPro I recommend taking some neon tape and putting it on the case. It's hard to see the thing when it's settled among rocks and crap on the stream bottom.