Orca

The Orca is a giant killer whale that pursues Sonic in certain sonic games. It is the first of many objects that Sonic must outrun in 3D sonic games

Sonic Adventure
The Orca first appears in Sonic Adventure in Emerald Coast. It chases Sonic across the wooden planks on the water in the famous "Orca Chase".

Sonic Heroes
Orcas appear in Seaside Hill jump over the road just beyond the third island. They are smaller than the first one and don't seem to have a grudge against Sonic