I've been using the GoPro Session cameras for 4 years now and have a simple routine that doesn't cost me more than 1-2 minutes of distraction all day while on the water. Everything is optimized for quick camera changes + recharging to maximize eyes-on-rods time.
I use the 1st-gen Hero Sessions (the cubes). They are $125 USD each, are waterproof (read: the audio is crystal clear -- no muffling due to a case), and can record 5.5 hours @ 1080P x 30 FPS on a 64GB microSD card. I could upgrade to the latest Session and get 4K recording, however battery life and length of recording will be shorter -- plus I think the HD video quality is more than adequate. The latest versions are well over $200 USD, too.
I have 4 cameras, but only need two over the course of a single day of fishing. Sometimes if I'm feeling adventurous, I'll use a third camera on a selfie-stick if I have a guest and want to send them home with some underwater footage of the fish or a separate camera angle. But mostly I use #3 and #4 as spares in case I forget to charge #1 and #2 or didn't download the video the last trip.
I have a single gooseneck mount directly above the bulkhead door on the cabin roof. The camera is pointed straight back and down a bit. The fisheye lens catches pretty much everything within ~160deg left-to-right and the entire cockpit and scenery (up and down). When bringing in a fish to the net, I try to net toward the stern if possible so as to capture as much of the action as possible.
Every 2.5 hours the camera battery will die and beep at you to replace it. I then unclip the camera from the mount and plug it into a portable USB charger I keep in the go pro case. I then hot-swap with the camera that was charging and clip it back into the mount. This swap-out takes all of ~20 seconds and you're back to fishing. Since the charging time is ~1 hour you can limit recording to just 2 cameras and minimize the number of cameras to download at home.
On the run back to the dock, I'll use the opportunity to wipe the cameras if there's no interesting footage and get them charged up for the next day. Back at home, I'll download only the 12 minute clips that are around the time of the footage I want to save. I'll save them in a folder with the date and location somewhere in the title. Then I'll wipe the cameras and charge everything up for the next day. After the seasons over, I'll sit down for a few hours and video-edit them down to single movies that capture the 20 seconds before the bite through the netting.
Besides keeping a log book of each fish I caught (tides, location, gear, etc), the use of cameras has significantly helped to catch more fish. Reviewing the footage of each strike has taught me that ~70% of my fish were caught because I did something different. i.e. turned the boat, changed speeds, came up/down 10ft on the riggers. You also get to review your mistakes, like horsing the fish in, dropping the rod tip, or not watching the rod when it's been bouncing for 10 seconds before you noticed. I keep video documentation of every legal sized fish I catch. To do this, the process of using cameras has to NOT be a chore -- and I think I have it dialed in pretty well. In total, I spend ~1-2 minutes on the water tending to the cameras and ~20 minutes at home saving video and clearing memory for the next day.
I've attached a couple pics of my cameras. The Go-pro case is not cheap ($50 USD) but is well worth the money, as it keeps everything tidy and easy to grab in the morning.
Hope this helps.
-Barry