Jordi Chias / Atolla jellyfish (Atolla wyvillei) with Gentoo penguin (Pygoscelis papua) in the background near the surface. Antarctic Peninsula. Finalist in the Underwater category of the Wildlife Photographer of t...

Norbert Wu / Jellyfish (Periphylla periphylla) being eaten by Anemone (Isotealia antarctica), Antarctica

Franco Banfi / Thimble jellyfish (Linuche unguiculata) aggregation, My Paradise Reef, Cabilao Island, Bohol, Central Visayas, Philippines, Pacific Ocean.

Franco Banfi / Thimble jellyfish (Linuche unguiculata) aggregation, My Paradise Reef, Cabilao Island, Bohol, Central Visayas, Philippines, Pacific Ocean.

Franco Banfi / Thimble jellyfish (Linuche unguiculata) aggregation, My Paradise Reef, Cabilao Island, Bohol, Central Visayas, Philippines, Pacific Ocean.

Sue Daly / Deep sea jellyfish (Periphylla periphylla), Trondheimsfjord, Norway, July.

Sue Daly / Deep sea jellyfish (Periphylla periphylla), Trondheimsfjord, Norway, July.

Alex Mustard / Hawksbill turtle (Eretmochelys imbricata) swimming up into the water column to feed on a bloom of Thimble jellyfish (Linuche unguiculata) in spring. East End, Grand Cayman, Cayman Islands. Caribbean S...

Norbert Wu / Jellyfish (Periphylla periphylla) in Antarctica, widely distributed and abundant in deep water, worldwide

Franco Banfi / Scuba diver with Helmet jellyfish (Periphylla periphylla), a luminescent, red, jellyfish of the deep sea, Trondheimsfjord, Norway, Atlantic Ocean.

Franco Banfi / Scuba diver with Helmet jellyfish (Periphylla periphylla), a luminescent, red, jellyfish of the deep sea, Trondheimsfjord, Norway, Atlantic Ocean.

Franco Banfi / Scuba diver with Helmet jellyfish (Periphylla periphylla), a luminescent, red, jellyfish of the deep sea, Trondheimsfjord, Norway, Atlantic Ocean.