After beating the Stingray I move down into the remnants of Walz Tower. Remember when I said to pay close attention when the tower was sinking? Well this is why. If you remember there was a crystal shard that was not accessible to us at the time. This was the Mime job's shard. In order to get it you must make it to the bottom of the tower before time runs out. There is a spot where you can refill your oxygen meter (the timer) about half way down.