Commensalism

Commensalisms are symbioses that are beneficial to one organism and neither beneficial nor detrimental to the other.

A common example of commensalism involves fish, often juveniles, and jellyfish. The juvenile fish swim around the jellyfish, presumably gaining something of a safe haven from potential predators. It is thought that the jellyfish is not affected by the relationship because it is not eaten by the fish nor does it eat the fish.