That pic is better but honestly, these things are very hard to ID unless they are common. I'm gonna throw out a guess to you that it's in the family Tritoniidae. So if I had to give it a name I'd say Tritoniidae sp. I know that's not very specific but that's the best I can offer. And again, it's just guess on my part. I'd be very watchful though, that it's not nibbling your corals. I see in this last photo it looks like it's checking out your soft corals.