The goby fish and shrimp
The shrimp builds and maintains a burrow that both animals live in and the fish offers the shrimp protection from predators. The goby just sits in the entrance of the burrow, keeping guard and warning the shrimp, which is nearly blind, with a flick of its tail, of danger. And before the shrimp emerges from the burrow, it touches the goby's tail with its long antennae. To show it is safe to come out, the goby gently wiggles its tail.