Photo Gallery: Planet Ocean

Earth's oceans cover most of the planet, but they are largely unexplored. Their seemingly endless expanses are home to creatures that range from the mundane to the inconceivable. Experience our oceans at their most compelling in this series of photos from Planet Ocean, a new book from National Geographic and the World Conservation Union.

Above, the Medusa-like arms of a northern basket star (right) seek a meal of zooplankton beside a polar alcyonarian soft coral in the shallows beneath an ice sheet in the Canadian Arctic.

Buy the book Planet Ocean for more photos.