Cyanea capillata is one of the largest species of jellyfish and is commonly referred to as Lions mane jellyfish due to the highly distinguishable mass of long, thin, hair-like tentacles. Cyanea capillata has a saucer-shaped bell (the umbrella) with a uniform thickness until thinning dramatically around the edges. Usually yellowish brown or reddish in colour. It generally grows to 30-50 cm in diameter in British waters. However, they have been know to grow up to 200 cm. The margin of the bell bears hollow tentacles, arranged in eight groups with 70 to 150 or more tentacles in each. The mouth and oral arms stem from a projection on the underside of the umbrella (the manubrium). The oral arms are thick, frilled, folded and generally as long as the diameter of the umbrella.Young Cyanea capillata may be found as early as February in British waters, although the main period of abundance for larger individuals is June to September. This species does occasionally occur in large swarms, largely thought to be due to storms and tides that concentrate individuals together (Russell, 1970). They have a very severe sting that can produce blisters, irritation, and muscular cramp and may even affect respiratory and heart function. Cyanea capillata can still sting long after being stranded on the shore.