[Scripting Question] Partner surfing and flying.

So in my game, I have a partner who needs to follow the player at all times, but the downside of it is that you cannot Fly nor Surf. I was hoping that there was a script out there, or if not, a way for me to script a way for a partner to deregister and then register itself once on land. I know that Pokemon Yellow did something like this, (not using the normal following Pokemon mechanics.)
So if you could help that would be great!