Sounds like you're shooting neck. Shoulders, unless you break both sides, are not reliable dropping shots, but they are positive kill shots.
This one could have made it to water.
Likewise.
I've always subscribed to high percentage shots (lungs). I can count the number of instant drops I've gotten on one hand - and two of those didn't involve broken bones! If I was going to be hunting where there was a decent chance of a moose going swimming, I believe I'd rather carry a come-a-long rather than hope to plant the critter in a spot of my own choosing.