"The Deepest Fear" is the seventh episode of the Sonic Underground television series. It first aired on 27 January 1999 in France and on 7 September 1999 in the United States. It was included in Volume 1 and Sonic to the Rescue.
The song performed in this episode is "Face Your Fear".
On a trip to Port Mobius, Sonic, Manic and Sonia are told that ships are sinking due to the Mobian sea-beast. The legendary story becomes fishy when the Hedgehogs meet Captain Squeegee who informs them of a scam in which townspeople must rely upon Robotnik for protection from the sea monster, when in reality it is Robotnik who is sinking ships, not a monster. Sonic must overcome his fear of water and the monster to find the truth and thereby ending the fears of the sea side town.