For diving we bought a cannon point and shoot then bought a housing. we paid $120 for the camera and another $150 for the housing. So for $270 we have a camera that is good to 150 ft for video or pics. I took several , 500, underwater pics with it. You can also get extra external flashes which we will do next time we dive.
If you are looking for cameras for fishing then there are a lot of choices. I was thinking of using our dive camera on a long pole to get shoots of fish figthing at the boat before netting. I also have plans to rig it to a crab pot in the near future.
there is a whole industry around video cameras on long 100 to 300ft cables that can be used under the boat or on the downriggers. For me the only really useful video for the downrigger is made by Walker downriggers and is part of the downrigger itself. One day I will have all the toys I want.