Hunting a animal on water looks like a glitch, buggy and reminds you: this is a simulation that isn't working properly.

Solutions:

drag option ~ drag your kill to the shore. You could do this many ways, from automatic, to a skill, to needing rope to tie around the animal to drag it while increasing your weight. Lots of options.

This drag option could be universal too, say you kill something yet can't harvest it right away, would be nice to be able to pull it somewhere safe you could harvest it, instead of watching it disappear cuz you can't harvest it quick enough with hostile animals around.

I think extending the time before a animal disappears would be extremely useful too, maybe double the time.