Just uploaded a update video on youtube:

Ideas to dehumidify the air inside the ROV to reduce fogging on the windows. The gas compensation air that will be pumped in at the start of every dive is likely to be wet. So I plan on circulating the air through a loop of copper tube that also connects to the AUX_pod:

The spear targeting laser would be easier to setup of the spear so I potted one to make it waterproof:

 Idea of using an OpenROV style etube to house the camera. It would be easier to make and would reduce the impact on the housing. But would reduce lateral vision and make it difficult to incorporate a tilt and pan mechanism for the camera.

Idea to create the AUX_pod from standard plumbing bits: 50mm MDPE pipe union, acrylic disk, rubber seal and tank connector. The connectors are also available in 75mm, if more space is required.

Idea of using cathodic protection for the copper, brass and motor metals. A small current could be passed through the metal -cathode through the water to a sacrificial anode. Would a passive anode protect the metal as much as an active system?

The Ole Hermann Godø 3d printed props are looking really promising.  They should provide more than twice the thrust compared to the props I was testing. 

I came across an OpenROV test on foam for ROV floats:

I was thinking about using the extruded Styrofoam- the pink one on this test. Unfortunately this test shows it shrinking under pressure. So I am know thinking about making the tether floats out of glass micro balloons mixed with resin or hot glue stick. If the hot glue and glass micro balloons combination is sufficiently buoyant it might be possible to make an extruder that could cover the whole tether?