Anyone know about electric engines that can be used down too 50 meters 12-24v with enough trust too move 25-40kg sideways ( have a wire from surface too hold it at the depthes needed ) ?
Hopefully a easy plugg and play engine !
Will use powersupply from surface

i would just experiment. There arent many manufactures that give depth ratings. The ones that do cost alot of $$$$$$

160 feet, I think you're on the wrong board. Try ROVs or deep diving robotics, or autominous underwater sensors, deep diving remote vehicles, maned/unmaned submersibles, scientific research vehicles, torpedoes etc.

Three ideas......
100 metres of 1mm square cable would have a resistance of 2 ohms.
Waterproof compression glands to fit a 6.0 - 6.35 mm cable would withstand 50 metres easily.
You could also pressurise a container by a foot pump or bicycle pump to 50 metre pressure.
Lee