Under the seas
This is an introduction to some of the weird and wonderful creatures found in our seas. 
The most primitive are the sponges which are found attached to rocks, plants and other animals. They are colonial animals (a group of animals living together in a colony although they may appear to be one organism). They come in many different shapes and colours like the bright orange ‘shredded carrot sponge' and the round spiky ‘yellow hedgehog sponge'.
The Cnidaria is a group of animals with stinging cells - jellyfish, anemones, corals and others. They are some of the prettiest animals in our waters, usually with soft fleshy bodies and long feeding tentacles. This year we saw large numbers of Portuguese man o' war jellyfish stranded on local beaches. That was unusual but we commonly see the flower-like dahlia and snakelocks anemones. Dead man's fingers are a soft coral often found growing on reefs and shipwrecks in our area.
Worms are commonly found burrowing in sand or muddy sediments. They often construct tubes to live in and feed with tentacles in the water column. Sand mason worms make their tubes using mucus to stick sand grains together! Some marine worms are beautiful, like the eyelash worm which can shoot back into its tube very rapidly if it senses danger. Others such as lugworms are rarely seen but the casts which they leave on the surface of the sand (produced during feeding) are common.
Crustaceans are the armoured tanks of the sea. Their skeleton is on the outside of their body and it protects their soft tissues inside. Lobsters, crabs, prawns and even barnacles fall into this group. Hermit crabs have less protective armour than most of their relatives and have to borrow old shells from other animals to use as their mobile homes! Squat lobsters hide in cracks and crevices and can ‘jump' backwards quickly to escape predators.
Sea shells, snails, slugs and clams all fall into the group called the molluscs. Molluscs almost always have a hard shell, although in a few animals like the cuttlefish you can't see the shell because it is inside them. Others, like octopuses have lost their shell completely, as they evolved. Sea slugs can be very striking and there are slugs with all manner of spots, stripes and colourful patterns. Here in Hampshire and the Isle of Wight we have some of the last remaining native oysters - a type of mollusc that lives between 2 shells known as a bivalve. Cuttlefish have incredible eyes and can instantly change colour to blend into their surroundings. You may find their ‘bones' washed up on the beach.
Sea mats or bryozoans are a strange group. They are colonial animals like sponges but are more advanced. They may live on other plants or animals or attached to rocks, they often look like plants because they may be branched or bushy. Potato crisp bryozoan (also known as ross) is a brittle orange animal which grows slowly in a rosette shape. Around here divers have seen some large colonies of this animal which may be over 30 years old.
The echinoderms (meaning spiny skin) are the starfish, sea urchins and sea cucumbers. Starfish like the bloody henry starfish and the common starfish which live in our waters are predators that move across the seabed using special organs called tube feet. Visible spines on the outside of urchins and on the skin of starfish and sea cucumbers are there to deter predators.
Sea squirts may form colonies or grow as individuals; they are filter feeders that live in a fixed position. If they're disturbed they squirt a jet of water by contracting their muscles quickly. Lightbulb sea squirts are often found around here, they have a bright band around them that looks like a filament.
There are many sorts of fish around here like the sharks and their relatives the rays. There are also the bony fish like pouting which often shoal around shipwrecks and the charismatic tompot blenny. Some sharks and rays lay eggs and their eggcases can be found washed up on local beaches.
We also get occasional marine mammals in our waters. There are common seals living in Chichester Harbour and grey seals sometimes turn up on our coast. Rarely we will get a sighting of a whale or dolphin such as this bottlenose whale that was stranded in Langstone Harbour this year.
More information on marine life and help with identification can be found at http://www.marlin.ac.uk/ .
Another good site for marine species ID is http://www.habitas.org.uk/.
