Torpedo Options

[TheRoadTrain]

Does changing between magnetic/inpact selection on your torpedo increase its chance when in stormy weather to actually impact the target instead of exploding on its way to the target?
Also which is best for inflicting most damage, going under the ships hull or straight into the side?
Cause ive noticed on some of the bigger merchants it sometimes takes 1 eel to drop them and the smaller merchants takes 2

Thanks people