I made the mistake of choosing the "Will call" ticket feature, which I've used before at the Shedd. Bad decision.
Thanks to the holidays, despite having purchased my tickets in advance, I had to wait in line for ~40 minutes just to pick them up. This was around 10:30am, and thank god it wasn't later, because by noon the regular ticket lines were at least 400 people long and the will call lines weren't much better.
ALSO: BEWARE BUYING THE WRONG TICKETS. Originally I'd meant to purchase a ticket that allowed me to go to the other exhibits, but this ticket (I belatedly realized) will only allow you into the most general parts of the aquarium and does NOT allow re-entry.