Though this doesn't have a lot of practical use, but it still doesn't seem intended :P You are able to mount flying mounts that normally you aren't able (Blazing Drake, Life-Binders Handmaiden, and the like.) in the water! Iitreally has no purpose but hell, it's cool!
https://i.imgur.com/tjh4L.jpg (the ticket response is from when my priest fell through the ground -_- )