I was gathering herbs and hunting on a remote lake, shot down a few birds over water, and as I waded in to pick them up and eventually started getting cold, I started thinking it would be useful to have a command for dogs to fetch prey floating on water. The dog would pick up the bird, come back and then drop it near the owner. Of course, if the dog was hungry, it would eat the bird instead. That might be expandable to other small prey as well - for example, you set your dogs on a hare, they hunt it down, kill it and then bring the carcass to you. The latter would be a bonus, but the former would be really useful especially in early spring/late autumn, when the waters are too cold to wade in yourself just to fetch a bird for a couple of cuts of meat, and you don't have a boat or raft handy.