
Discover the fascinating creatures that inhabit our vast oceans. These cold-blooded vertebrates have gills, which are specialised organs allowing them to breathe underwater.
Stingray: © Galaxim via Unsplash
Leaping salmon: © jl123 via Shutterstock
Shark: © mapush via Shutterstock
African Catfish: © Marcos Campista via Shutterstock
Catfish: © J. Michael Jones via Shutterstock
Mekong giant catfish: © Danny Ye via Shutterstock