If you want to skip the lines, which can get really long especially during weekends, it's best to get the Georgia Aquarium: Fast Track ticket. This will let you float on past the crowds like a jellyfish and straight into the aquatic action. It'll get you admission to all the galleries, including the 'Sharks! Predators of the Deep' Gallery.
You can also get Georgia Aquarium tickets as part of the Atlanta CityPASS, along with admission to the World of Coca-Cola and a selection of the city's other top attractions, including Zoo Atlanta, the National Center for Civil and Human Rights, Fernbank Museum of Natural History, and the College Football Hall of Fame.