If you are hunting close to water you might want to consider shooting your bull right on top of the shoulders. That will drop him on the spot minimal meat loss. Beats having them run out into the lake and falling over.
Trying to figure out where you mean to shoot... but not liking the sound of it much. The dorsal processes on a moose spine through the shoulder region are VERY long.
I have shot a couple moose just above the spine through the shoulders and do not suggest it. Both bulls went down instantly, but were hardly "anchored" in the sense of unable to get into water or worse...
The biggest, perhaps most reliable "tip over" shot may just be the pelvis. That won't mean he'll quit, but he won't be mobile anymore. I would certainly want an E-Tip, TTSX, GMX or something along those lines if that was on my agenda though (to avoid or minimize meat loss). Same deal if I was trying to take the much iffier shot to take out both scapula/humerus joints - it works very well and is quickly lethal as well, just a very difficult shot to pull off intentionally.
Of course there's also the brainer shot as long as antler width isn't a legality issue; not liking the drawbacks unless it's a close shot however. From what I have seen, they seem to be quite willing to stand there and bleed when one front leg is useless and both lungs are ventilated. But then, I don't generally shoot them when they are tempted to swim either.
