Is it Shoopuf? (yeah just like the chocobo)

I am used for a while - at moonflow, to cross the river
Then I'm left behind - after that they depart
I am not seen much again - um that was the last time they ever saw a shoopuf
I'm used to protect lives - right....
But my owner is strong enough to live without me - the blue alien creature are their masters.... aaaannndd... ahh... :/