Porcelain crab which lives in symbiosis with the sea anemone -- mouth parts with plankton net (Comoros).

 

Pacific Jack shelters under the wings of a Marbled Ray so that he is invisible to his prey. In fact, the Marbled Ray gets him close to his victim (Cocos Island).

 

Medical service in the sea. In order to signal that they suffer from itching parasites, the normally yellow Goat fish turn red for the black and yellow French Angel fish which cleans other fish of parasites.