high def camera with DVR and sensors

My boss has a fishing boat, goes out in the ocean and does the whole catch huge Tuna and Marlin thing.
he wants to put two waterproof high def camera on the top of the boat, connected to a DvR for recording.

I am looking at what is needed to add sensors on the boat to activate the cameras and start recording.

need a couple 'start' buttons around the boat.

anyone use high def cameras and dvr that can be used on a boat ? (120VAC)
suggestions on equipment and mounts and such ?

waterproof switches (salt water)
the enclosure for the electronics will most likely be in a Pelican case or NEAM4, gasketed case.

I know what I am looking for at the start is more hardware based, but I need to get that part sorted out so I know what is needed for control and then can do the software parts.

Anyone interface with a DVR ? links, recommendations ?