It's a dud - again!

[bcarter3]

So I upped my difficulty a little from easy so that I now get dud torpedos, and boy did I get some duds. I fired off 10 torpedos, all ten hit the mark, 7/10 were duds! Is this normal? How many duds should I expect to get? This seemed a little high to me. Heck, if 7/10 are going to be duds every time I might as well surface the dang boat and pop off deck gun shots, I might even hit something then!