It would be a nice feature if you were to make it so if you get close enough the sharks actually follow you :)
Okay, I just uploaded a new version of Immortal with the gameplay change you suggested. When a shark is swimming toward The Jelly and is close to it, it will now move up or down to get to the same height as The Jelly. I think this will make gameplay a bit more engaging.
Please try it out and let me know what you think.