Wireless connections are cool and all, but sometimes you just need a bit of copper. This interesting article on SV Seeker discusses the various ways of making a tether for a remotely operated vehicle (ROV). They experimented with a number of different cables, including gel-filled Cat 5 designed for burial and wrapping the cable in polypropylene rope to keep it protected and buoyant. They also looked at using a single core solid coax cable with an Ethernet to coax converter on either end wrapped in stretch webbing. The upside of using coax would be the length: it can handle over a mile of cable, which should be more than enough for this project. The downside is that they found that the coax stretches under strain, messing with the signal.
The project seems to be on hiatus at the moment, but there is lots of food for thought here for anyone looking to send data over a long distance. I’m looking to put a webcam in an owl box in my back yard, and I hadn’t come across some of the options they cover here, so I’ll be looking into direct bury rated Cat 5 myself.