[3] They are found typically in late summer, and early fall in increased populations which are known as blooms.

It typically is up to 40 cm (16 in) in diameter, but can exceptionally reach 150 cm (59 in) or larger,[7][8] making it the largest jellyfish in British and Irish waters (Cyanea capillata reaches an even larger size, but is generally smaller in Britain).

On 13 July 2019, wildlife biologist Lizzie Daly dived off the coast of Cornwall in the United Kingdom, along with the underwater cinematographer Dan Abbott.

Effects include a burning sensation on the skin, dermatitis, and ulcers which confirms it is toxic to humans.

[13] One study indicates that washing in aqueous solutions and the separation of high molecular weight proteins from the extract, e.g., by membrane filtration, could be a way to remove possible toxic compounds from jellyfish extracts and to concentrate potentially bioactive soluble compounds.