Jaws Rek'Sai
Imagine playing League and out from the jungle you see a giant dorsal fin coming out after you and the music changes to the Jaws music in the background of anyone in vision of Rek'Sai. then out pops a shark like version of Rek'Sai. When a shark senses vibrations in the water it recognizes it as prey, making the ripples red to also represent blood would be cool too, this goes along with her ability to sense where enemy champions are on the map. Her tunnels could change to small bodies of water, her poke would be a blast of water, changing her borrowing to shark like animations, sharks bite so that fits perfectly and for her ult using the blood chilling scream that follows the jaws music in the movies to signal enemies that terror is on the way.
I also like the skin idea, Great White Rek'Sai