Lynn wants to join the military, but is unable to because women aren't allowed. She is stuck in a city underwater surrounded by glass. Her brother on the other hand has already joined the military and is sent on his first mission. But what will happen when Lynn's brother goes MIA (Missing In Action) and no one bothers to look for him? She takes matters into her own hands. But the danger in the sea are not just sharks or killer whales. They included creatures that have been unknown to man. A whole civilization, it's Aquion.