"Aquatic Animals" is the third episode of the A series of QI. It first aired on 18 September 2003 on BBC Four, and aired on BBC Two a week later. The episode was the second to feature Bill Bailey (after "Astronomy"), not including the Pilot. It marked the first time a guest panellist had appeared in two episodes in a row. The previous episode was "Astronomy" and the next episode was "Atoms".