You will get knocked off your griffin if you touch water! When I was flying I accidentally touched water and there just so happened to be a high level megalodon right below me and I think you can guess how that turned out.
imo these are the BEST flying mounts in the game because you can hold 2 people and shoot of of its back along with their maneuverability, speed, damage output, stamina, dive bomb, 2 special attacks, and health. I'm currently leveling up my griffin and so far it has 500% damage, 1500 stamina, and 15k health and there is practically nothing that can take it down. (also, its dive bomb swipe attack does over 1000 damage!)