On Sight! The Sunken Ship in Southern Sea
From Sonic Retro
On Sight! The Sunken Ship in Southern Sea is the 16th episode in the first season of Sonic X. In the English dub, it is known as Depths of Danger.
Chuck Thorndyke gives Sonic, Tails, Amy, Cream and Chris passports so they can travel. The five decide to go to the Southern Sea for a vacation. While piloting the X-Tornado, Tails detects the presence of another Chaos Emerald, but it's underwater.
While Tails, Amy and Cream are playing on the beach, Chris tries to help find Sonic an air supply so he can stay underwater and search for the emerald, but he fails. Realizing that the only way they can stay underwater is to rent some scuba gear, Chris brings Sonic, Tails, Amy and Cream to a dive shop, the shopkeeper of which tells them about a legend of a nearby sunken ship that's filled with treasure. Sonic and his friends dive underwater and find the ship, treasure, and dark blue Chaos Emerald.
Meanwhile, Eggman finds out Sonic is on vacation. Eggman, who is upset that he can't go on vacation, sends E-57 Clurken, a large, jellyfish-like robot, to defeat Sonic for revenge. Tails, Amy, Cream and Chris return to the surface as Sonic attempts to battle the robot underwater. Sonic can't swim very well, much less fight underwater, and he gets blown to the surface. Suddenly, Sam Speed arrives on a jet ski and helps Sonic by letting him water-ski behind him. Tails gives Sonic a power ring, which Sonic uses to defeat Clurken. In the end, Sonic and his friends finish their vacation.