In Sonic Adventure, what is Sonic's first action stage called?

In Sonic Adventure, Sonic's first action stage is called Emerald Coast.

After the opening events in Station Square, Sonic heads to the seaside to investigate Tails's crashed plane. Emerald Coast is the first full action stage in Sonic's story, introducing the game's shift from the classic 2D format to fast, three-dimensional platforming.

The stage combines beaches, ramps, loops, springs, narrow platforms, and a famous chase sequence involving a giant killer whale. Its design quickly demonstrates Sonic's homing attack, momentum-based movement, and the Dreamcast game's emphasis on cinematic set pieces. The goal is to reach the end and find Tails near his wrecked aircraft.

Emerald Coast is sometimes confused with the game's Adventure Fields, especially Station Square, where the player explores between stages. Station Square is a hub area, not an action stage. Other listed choices appear later in Sonic's route: Windy Valley follows Emerald Coast, while Twinkle Park and Speed Highway occur later in the story. The stage also appears in other Sonic releases, including the Nintendo 3DS version of Sonic Generations.