I purchased in 2012 a couple of video cameras that were the size of USB thumb drive. After looking at the quality of these videos I wondered where they could be used. As I thought it occurred to me that they could to be in a water proof enclosure and they would were small enough to attach to a fishing line. This way the video would capture the bite and the fight (credit my wife with that turn of phrase).
I am a chemist so I know how to build low pressure systems to use in the lab, but not one to be leak proof at 500 Feet in the water. I was talking to a guy who said to use the Parker O-ring handbook to design you enclosure and seals. You can make a good enclosure with simple a metal lathe and being able to cut plastic to the proper dimensions.
I purchased video cameras (720Pp) from Alibaba that I connected to some AAA batteries. This was perfect when I used a 32 GB microSD card and the batteries it filled ~28GB in 4 hours the same as the batteries. Also, you could swap the batteries and microSD card in 10 minutes or less and keep collecting video.
If you are interested in capturing the video of the fish bite and fight underwater? I will show you how to do it cheap and how to turn it into many things beyond the simple video.
https://www.parker.com/Literature/O-Ring%20Division%20Literature/ORD%205700.pdf Read section 3 on static O-ring sealing if you want to design your own system