Sorry, I couldn't resist. I immediately remembered that scene from the movie.
If I am not mistaken, I think that they are going to release the Lily pad on the next expansion with an effect similar to what you said. (It will make any plant amphibious and give it 1 extra health, however it doesn't bounce back).
I think that zombies got also a card that made zombies amphibious but I can't remember.
I like your idea, but I disagree with the part about bouncing the card back. It should be a card like the Yeti Lunchbox that you can use it only one time. However, we can invent a card like... Floater Seller Zombie that conjures you more floater cards. I think it is more fair and more fun as well.
However, good idea my friend. Let me give you some XP.
