Just came across BlueRobotics and this forum! Great things you are doing here.
I noticed some interest in Drop Cameras so I thought I would share my build, and some videos from the past few years.
I started off building an ROV, but changed gears after realizing an ROV was not feasible for what I wanted to do. There were some areas that I wanted to film that were from 300’ to 1200’ deep. With my boat, there was no way I was going to get an ROV down there easily and accurately, so I built a large towed (very slowly) camera sled that holds 2 GoPro’s, multiple life feed cameras, depth and temp sensors, and a ton of LED lighting. I burn through the 30 amp hour battery pack in a little over an hour with all lamps turned on. All of the data is transmitted over RS485 on one pair, and one channel of live video on the other pair in a CAT 3 style cable. I use amsteel blue for the strength member with the cable. The whole sled is about 80 lbs (on land) and I built an electric winch to reel the 1500’ of cable up and down. Its quite the operation to deploy and retrieve, but the video comes out pretty good. Enjoy some of the video clips I have put on youtube: https://www.youtube.com/user/NPerry8051
A lot of what I learned building the first ROV was used in the design of the sled. Really the only difference is the lack of thrusters and neutral buoyancy.