Ecco the Dolphin: Defender of the Future is an action-adventure game released for the Sega Dreamcast. As a sequel to the classic 2D side-scrolling Ecco games, it transitions into a fully 3-dimensional underwater experience. Players navigate Ecco, a bottlenose dolphin, through an aquatic world filled with puzzles, enemies, and elaborate environmental challenges. The game is known for its stunning graphics, intricate sonar-based mechanics, and a captivating storyline involving time travel and an epic battle to save the ocean from a dystopian future.