This was my first night dive and we took it down to 55'. During the dive we ran into an issue getting the tether snagged on something and we had trouble moving forward after about 20 min into the dive . I had 3 ping pong balls on the tether to have it float about 30' of tether up off the bottom but I had about 120 feet out, so the tether from about 40' to 120' probably sat on the bottom and got pulled across the floor as the ROV went further away and likely snagged on debris Later dives I added 3 more to get about 65' to be slightly + buoyant. When I got back home I bought 6 more ping pong balls so I should be able to float 130' of tether on my next dives. The need for a floating or neutrally buoyant tether is something that I hope someone will come up with. I also discovered that I need a light facing down under the ROV to improve the lighting, this is one advantage the OpenROV project has as the lights move with the tilt of the camera whereas mine do not. On some other night dives I mounted a small led water proof flash light pointing down which had a narrow beam. This turned out to be very helpful, not so much for lighting up the bottom floor with the camera tilted down but for seeing you approach the bottom. What had happened as I descended in total darkness I could see the beam of light pointing down from the ROV, as I neared the bottom the light beam circle became bigger and bigger so I new the bottom was approaching. It will be interesting to see how your laser led's will work in this environment in detecting the bottom as you get closer. Unfortunately I lost a few real nice dive recordings because my batteries on the laptop died before I could close off the screen capture software to save the file. This is another topic that needs more discussion on, what is the best recording software to use etc so I will leave that to a different thread.