Big Swell takes place on a warship owned by Captain Whisker amidst a sea with black and sharp outcrops. The sky is overcast by black, purple and orange thunderclouds, creating a dark atmosphere. The ship itself is without a superstructure, but has a raised stern with a fence, an orange deck, a socket for the Ghost Titan, and a hazard stripe-marked strip. It is also armed with large turrets/cannons, and spotlights in the deck shoot light columns into the sky.
When Sonic and his allies reached them, Whisker was about to "torture" Marine with the Ghost Titan. As Whisker negotiated Marine's freedom with Sonic and Blaze however, Tails distracted the pirates by saying that their stolen Jeweled Scepter was elsewhere while Sonic and Blaze saved Marine. Proceeding to engage the Ghost Titan, Sonic and Blaze defeated it, causing it to explode. However, Sonic and Blaze outran the explosion that destroyed the ship, sinking Whisker and his crew.
Viewing the burning wreckage from afar on the Deep Typhoon, the group scolded Marine for going after the pirates on her own, who apologized for her rashness for the first time. Just as the group pondered on what happened to the Jeweled Scepter however, Marine revealed that she took it back, making some amends with her friends. With Captain Whisker defeated and the treasure reclaimed, the heroes headed back to Southern Island.
The boss of Big Swell, and the only playable section of this stage, is the Ghost Titan, the largest robot in service to Captain Whisker. It can be fought immediately after entering Big Swell.
In battle, the Ghost Titan attacks with guns, laser cannons, missiles and its fists. Regarding its cannons, it can either fire them from afar or detach them and have them fire at the player up close. It can also either launch its fists at the player from afar or get up close for a barrage of punches. To damage the Ghost Titan, the player must use the hostile cannons in the arena to fire the characters into the Ghost Titan's head. Sometimes however, the cannons will be surrounded by a force field, which the player must lure the Ghost Titan into destroying. Keep hitting the Ghost Titan's head until it collapses and land the final hit as it destroys the arena.