that'd be about it right there.
they are lucky he wasn't a bit less tired they coulda been the ones needing a rescue.

Usually roaming domestic dogs or coyotes are the reason deer take to the water. But usually there’s an island or peninsula much closer than that. Apparently that deer’s plotter wasn’t working properly. Many years ago I spotted an otherwise healthy looking buck one summer dead on the shore of an island. Bite marks all over his hind quarters. Looked like he hauled himself up on the seaweed and died of exhaustion. Seen moose and deer swimming in the ocean while lobstering on a couple of a occasions