I know, I know, this has been discussed. Just throwing it out there as a friendly reminder of how useful it would be for traveling.
We can carry boats (row and dugout) across land when traveling, so why not let horses cross water? Just dismount and leash them, and they will follow you where you swim - much like entering and exiting a cave. Of course drowning dangers would apply for both horse and rider. And no fancy stuff needed (such as also dragging a cart or other animals across.)
Just a simple fix to greatly (and realistically) enhance cross country travel. Maybe apply to other livestock (any leashed animal), but for me, just horses would be great. Just horse and rider (hmm...maybe no dismount? I've wondered about why you need to dismount to enter a cave but not a mine hole - a house but not a gate? ... just musing - computer code doesn't always translate I suppose.)