Sea jellies are also called jellyfish. Large ones are often washed up onto the beach. Their bodies are bell-shaped. Some muscles and nerves help sea jellies to contract their bells and push themselves through the water. The edge of the bell can have tentacles. They have just one opening into their stomach.
Bluebottles are a colony of many animals. They have a float that helps them drift on the surface of the sea.
A tiny sail at the top allows the wind to push them around. The wind can push thousands onto the beach. Different members of the colony are specialised to do different jobs. Some members make up the float. Others use their stinging cells to defend the colony; others catch food, digest food or are involved in reproduction. The long strands below the float are the animals with the poisonous stinging cells.
These animals have stinging cells. Barbs are fired from cells. The barbs have poisonous chemicals that will kill small animals and can be harmful and painful for people. Bluebottles only need to brush the skin to cause very painful red marks.