Here's a couple of pictures Ron has been posting up on the Dive-in facebook page-
This is one of the tanks, which slots into the end of the cylinder. It's a lexan cylinder with a cast polyurethane piston, and an o-ring seal. The piston runs up and down on the shaft. Note the use of helical gears for strength and quieter than spur gears.
Ron says that retract speed is about 3 seconds!! Current used is 1.5A at 6 volts, so 9 watts, or 18 watts for both tanks. Bearing in mind they only operate for a very short length of time, this system is not at all thirsty.
This is the motor pod. With the system Ron uses. It's not practical to mount a drive motor in the main WTC, because the rear tank gets in the way, so it gets its own little module.