There are rich sponge communities on Scilly's rocky reefs.
Sponge community, Tim Allsop
These all have stinging cells and include anemones, corals, hydroids and jellyfish.
Sunset coral, Tim Allsop
These all have their own armour and include crabs, lobsters, shrimps and barnacles.
Crab, Fiona McNie
Worms are common in the marine environment, often they are found burrowing in mud or sandy sediments.
Worm and cast, Abby Crosby
Tiny and delicate, often found in shallow water amongst seaweed.
Sea shells, snails, slugs, bivalves, cuttlefish and octopus are part of the largest group of marine animals called molluscs.
Sea slug, Tim Allsop
These are colonial animals and may live attached to rocks or grow on other plants and animals.
Potato crisp bryozoan, Tim Allsop
Meaning 'spiny skin' and inlcudes feather stars, starfish, brittlestars, sea urchins and sea cucumbers.
Starfish, Tim Allsop
These are filter feeders that live in a fixed position and can be colonial or live as individuals.
Light bulb sea squirts, Tim Allsop
There are bony fish and cartilaginous fish such as sharks, skates and rays.
Blenny, Tim Allsop
Sea turtles are occasionally seen offshore and in deep water off the Isles of Scilly and the mainland.
Leatherback turtle stranding, David Mawer
The Isles of Scilly are visited by a number of marine mammals and is a stronghold for Grey seals.
Common dolphins, Robin Mawer
Seaweeds and flowering plants
Plants are important in the underwater world of Scilly. There are many different seaweeds and seagrass which can flower underwater.
Diver surveying seaweed, Claire Goodwin
From rocky reefs encrusted with delicate and colourful invertebrates to golden green seagrass meadows on white sand, the marine life of the Isles of Scilly is unrivalled in vibrancy, diversity and health.
The seas around Scilly are clean and clear, and beneath the water (amongst hundreds of shipwrecks) lie bright gardens of jewel anemones, sponges, corals and sea fans, kelp forests and prairies of sea grass.
The seas are home to a huge range of creatures: Grey seals, Dolphins and Porpoises, Basking sharks and even more exotic visitors like Ocean sunfish and Leatherback turtles.
The marine environment worldwide is under constant and growing threat, and Scilly is no exception. The Isles of Scilly Wildlife Trust works closely with the Isles of Scilly Area of Outstanding Natural Beauty to deal with massive quantities of floating plastic, rope and other debris swept in from the Atlantic.