Based on crayfishes, Yagos have torpedo-shaped bodies. They have small black eyes with an orange head section, black rims around their eyes and a small gray jaw. Their lower body is heavily armored with a pair of orange claw-arms covered in armor too, and a black rear which has a gray turbine for propulsion attached. Decayed Yagos show an alternate color scheme, having yellow-green and blue armor instead of orange and gray.
In Sonic the Hedgehog CD, Yagos appear only in the water sections of Tidal Tempest. In gameplay, they swim along the sea floor very slowly. When they spot the player though, they will suddenly lunge toward the playable character. The player can easily dodge this attack by jumping before then counterattacking.
In the Bad Future or sometimes the present timeframe of the Round, the dilapidated Yagos have an arched body and broken armor. They also move slower when attacking. Like every Badnik in the game, they are powered by Little Planet flower seeds which will pop out of them when they are defeated.
"Yago" (ヤゴ,"Yago"?) is the Japanese word for "dragonfly larva".