Shane Gross / Black grouper (Mycteroperca bonaci) with Remora fish (Remora sp). Caribbean Sea off Gardens of the Queen National Park, Cuba.

Tony Wu / Pygmy blue whale (Balaenoptera musculus) at surface, before diving to forage on krill, Sri Lanka, Indian Ocean.

Henley Spiers / Green turtle (Chelonia mydas) juvenile, swimming in open ocean, with two Pilot fish (Naucrates ductor) and a Remora (Echeneidae) swimming alongside, Eastern Pacific Ocean. Endangered.

David Hall / Giant oceanic manta ray (Mobula birostris) with two Remoras (Remora sp.) swimming underneath, Socorro, Revillagigedo Islands, Mexico, Pacific Ocean. Endangered.

David Hall / Giant oceanic manta ray (Mobula birostris) with two Remoras (Remora sp.) attached underneath, Socorro, Revillagigedo Islands, Mexico, Pacific Ocean. Endangered.

David Hall / Giant oceanic manta ray (Mobula birostris) being followed by two Remoras (Remora sp.) and a group of Clarion angelfish (Holacanthus clarionensis), Revillagigedo Islands, Mexico, Pacific Ocean. Endange...

David Hall / Giant oceanic manta ray (Mobula birostris) with two Remoras (Remora sp.) and shoal of Black jacks (Caranx lugubris) swimming alongside, Socorro, Revillagigedo Islands, Mexico, Pacific Ocean. Endangere...

David Hall / Giant oceanic manta ray (Mobula birostiris) with a Remora (Remora sp.) and two Black jacks (Caranx lugubris) swimming beneath it, Socorro, Revillagigedo Islands, Mexico, Pacific Ocean. Endangered.

David Hall / RF - Giant oceanic manta ray (Mobula birostris) with two Remoras (Remora sp.) attached swimming over volcanic rock, Socorro, Revillagigedo Islands, Mexico, Pacific Ocean. Endangered. (This image may b...

Lucas Bustamante / Giant manta ray / Oceanic manta ray (Mobula birostris) with two Remoras (Remora sp.) swimming on dorsal side, Isla de la Plata, Manabi, Ecuador, Pacific Ocean. Endangered.

Doug Perrine / A large female Tiger shark (Galeocerdo cuvier) with crooked jaw likely from fishing interaction, and a remora or sharksucker on her chin, swimming above Bluestripe snappers (Lutjanus kasmira), Honoko...

Doug Perrine / Tiger shark (Galeocerdo cuvier) with remora / sharksucker attached to lower jaw, and nictitating membrane partially covering eye to protect it; shark has slight injury to eye socket, revealing more of...