A rocky shoreline covered with clusters of blue-black mussels. The mussels cling tightly to the rocks, creating a textured surface. Some green algae is visible in the water pools among the rocks, reflecting sunlight.

Citadel of Sacsahuayman, a native Inca complex surrounded by walls that were made by fitting stones tightly together without mortar, UNESCO World Heritage Site, Cusco Region, Peru, South America

Tightly coiled fern frond (fiddlehead) in the rainforest on Tenorio volcano, Volcan Tenorio National Park, Alajuela, Costa Rica, Central America

Citadel of Sacsahuayman, a native Inca complex surrounded by walls that were made by fitting stones tightly together without mortar, UNESCO World Heritage Site, Cusco Region, Peru, South America

Close-up of a mass of king penguins (Aptenodytes patagonicus) in a tightly packed colony at Volunteer Point, Falkland Islands, South America

Tightly balled school of jack fish, South Point, Sipadan Island, Sabah, Malaysia, Borneo, Southeast Asia, Asia

Cattle crammed tightly together in a pen at cattle auction in Ennis, County Clare, West of Ireland

Young calves crammed tightly together in a pen at cattle auction in Ennis, County Clare, West of Ireland

False killer whales (Pseudorca crassidens) tightly bunched group streaming bubbles, Azores, Portugal, Europe

Group of tightly bunched false killer whales (Pseudorca crassidens), Azores, Portugal, Atlantic, Europe

False killer whales (Pseudorca crassidens) tightly bunched group diving vertically, Azores, Portugal, Atlantic, Europe

False killer whales (Pseudorca crassidens) tightly bunched in a sea full of bubbles that they have created, Azores, Portugal, Atlantic, Europe

Group of tightly bunched false killer whales (Pseudorca crassidens), Azores, Portugal, Atlantic, Europe

The pointy snout of a surfacing Minke whale (Balaenoptera acutorostrata) keeping its blowholes tightly closed until the moment they break the surface. St. Lawrence estuary, Canada

Fraser's dolphin (Lagenodelphis hosei) Tightly bunched Fraser's dolphins traveling at speed. Eastern Caribbean

Bell hydroid (Tubularia larynx) large group of individuals tightly packed togethe clearly showing polyp heads, St Abbs, Scotland, UK North Sea

Minke whale (Balaenoptera acutorostrata) surfacing in the green coloured water. Although exposed, she still has both blowholes tightly closed. Note the pronounced ridge on the rostrum, a main feature of rorqual whales. St. Lawrence estuary, Canada Sequence 1/2.

Fraser's dolphin (Lagenodelphis hosei) A typical tightly bunched group of Fraser's dolphins. Eastern Caribbean

Tightly overgrown coastal forest at sunrise in Queen Charlotte Sound, Marlborough Sounds, Picton, South Island, New Zealand, Oceania

Chicken chicks, tightly packed in boxes at the market, Morocco, Africa

A single calf tagged 162 looking straight at you cropped tightly; Eastend, Saskatchewan, Canada

Close up of tightly packed microgreen coriander seedlings shot from above

Close up of tightly packed mustard microgreen seedlings shot from above

Close up of tightly packed garlic chive microgreen seedlings shot from above

Close up of tightly packed Amaranth Aztec microgreen seedlings growing

Close up of tightly packed pea seedlings growing in urban farm

Tightly packed Amaranth Aztec microgreen seedlings shot from above

Close up of tightly packed pea seedlings growing in urban farm

Tightly packed Amaranth Aztec microgreen seedlings shot from above

Close up of tightly packed microgreen seedlings in urban farm

Close up of tightly packed coriander seedlings growing in urban farm

Side view of tightly packed pea seedlings growing in urban farm