...especially gut-shot deer. They, like us, absorb almost all of their moisture through their large intestine, and if it's blown apart, or the digestive tract is sufficiently dammaged ahead of the colon, and the deer lives long enough, it'll get plently thirsty.

My other thought was that they could have fallen through the ice, but I was in a different boat trying for big fish of the night, so I didn't see how deep he was or how he was laying.

Just take up bowfishing and shed hunt as you go.
You can do it with any bow once you add a few accessories and special arrows.