Actually, it depends on your point of view. A modern torpedo has a sensors, a drive system, and travels through the water. The only "torpedoes" that don't qualify as vessels are the old old old ones (think Revolutionary war, Spanish-American war) that were what we today would call mines. Technically, there are very few underwater missiles. The Russians have some, but they are more dangerous to the sub firing them than to an enemy. Everyone else uses some form of propeller-driven torps.
I'd like to suggest a small change to the original idea that started this thread that includes the fish hooks. Deploy the fish hooked lines attached to a bobber the same way that mines are deployed. This would make them anti-submarine mines.
I thought they had problems with a hydrogen peroxide powered torpedo. Either way an explosion in your submarine is never a good thing.
I'm not sure what fuel they were using, I just know it was a rocket-propelled torpedo. H2O2 is a good fuel for rockets, but I would expect them to use one that would last longer (without deteriorating in storage) for a weapon that would likely sit in torpedo racks on a sub for years at a time.
Well it is indeed an interesting idea, but not a whole lot can touch a sub under water, the only possible way i can see is either the use of pyrotechnics or using guns pointing directally downward, so you would have to drive right over the sub to hit it (verry similar to real depth charges)
Pyrotechnics are strictly illegal for safety reasons (don't want to risk blowing off your hand when you swim for your sunken ship). Cannons pointing directly down have also been tried, but never could penetrate the impenetrable deck of the submarine. Fortunately, the difficulties of anti-submarine warfare are made less important by the fact that every warship can outrun a submarine.
