I'd suggest getting a Chicago Go Card or City Pass just to skip the lines... they are freakin' insane! Honestly, wasn't that impressed... there are just too many people crowded in there to enjoy it.
Strap a mask and flippers onto your imagination and chart a course to Shedd Aquarium. Have you ever gotten eye-to-eye with a dolphin? Or met a penguin on a stroll to the South Pole? Or immersed yourself in an Amazon flooded forest? At Shedd, it's all possible.