You can create a macro to chosese between smimming and flying mounts:
/use [flyable] FlyMount
/use [swimming] SwimMount
/dismount [mounted]
But some mounts are allowed only in specific area. For example, Vashj'ir. If I'm out of Vashj'ir, then even if I'm swimming I want to mount a FlyMount, since it has some use (I can fly out of water). Is there a way to do it?
Best Answer
You could probably add a modifier to that macro:
This should mount sea turtle with no mod pressed while swimming and with alt pressed while swimming should mount Invincible. I am at work so I cannot test if it works but I don't see why it wouldn't work.