It did fly off in a similar matter although i didn't see it bounce off anywhere else, maybe it did all that underwater

To clarify on exactly what i did, although i'm unsure whether this will replicate it.
I rode my horse all the way up to the gate, remembered i had to dismount to enter the city. turned around and stopped the horse exactly ontop of a short set of steps (the horse was standing diagonally) and then i just dismounted. no sooner had i got one leg over did it launch over the wall of the bridge, fly a few hundred feet and then splash down into the water.