Decades ago Cavalero Champion manufactured a gadget to retrieve shooting line on their euroguns, it was called the "Line Gobbler". I remember seeing them for sale, but never bothered to really examine one. Recently someone mentioned an old article about them in Skin Diver magazine which shows how they work. Basically they can store and retrieve about 10 feet of shooting line in a tube that is essentially a water pump. The shooting line, a woven cord type, pulls out from the tube during the shot, which does not sound like such a good idea, but it is the retrieve that is interesting. When you operate the water pump it creates a vacuum that sucks water in the front end and with it the shooting line which goes in with the water. Each pump stroke sucks in more of the line. On pushing the pump handle forwards each time water in the pumping chamber just squeezes out past the small hole in the front as the hole does not seal tightly on the line and the water can escape.
I thought that I would mention it here as probably most have never heard of it, or have completely forgotten about it. Possibly the concept could be used in other applications where one wants to retrieve line underwater without cranking a handle on a drum or wrapping it end to end on some stowage hooks.
I have yet to find the patent for it. (1982 vintage)