My grandfather gave me this sword a few years back and told me that it was used by submariners in WWII. That's all the info I have on it and was hoping someone could give a more detailed history. Album below, thanks all!
Looks like it's a Model 1917 Naval Cutlass. They weren't manufactured in large numbers or issued for service, but some unofficial variants of the same model were used (mostly for ceremonial purposes) and most of them ended up just being sold as surplus after WWII.
The emblem on the cross guard looks like someone glued a U.S. Navy Submariners emblem on there, as that wasn't standard. Also the hand-grip was originally wooden, but from your pictures it looks like it's are wrapped in some kind of tape.
He didn't happen to give you the scabbard with the cutlass as well, did he? If you had some pictures of that as well as some closer ones of the hand guard, I might be able to tell you more about it.
Here's a good read on U.S. Navy Cutlass's if you're interested, http://www.history.navy.mil/library/online/uniform_sword.htm