StatisticsOval float up to 10 cm in length but usually smaller
When to seeSeptember to March
AboutThis incredibly strange and beautiful species is known as a colonial hydroid. They are similar to the Portuguese man o war as they are made up of a colony of tiny individual animals. They are not true jellyfish.
Its characteristic sail gives the animal its name, 'by-the-wind-sailor'. The sail allows the organism to catch the wind and travel on ocean currents, using its stinging tentacles to prey on young fish and other small animals while it travels. They are at the mercy of the winds and so are usually found washed up in their hundreds, or sometimes even thousands, after stormy winter weather.
How to identifyThese small organisms consist of a deep bluey purple oval disc, known as a float. A thin, semi-circular fin (sail) attaches diagonally across the top of the float and tiny short tentacles hang down from the float into the water below.
DistributionA pelagic (open ocean) species commonly recorded around British and Irish coasts in the autumn and winter-time when storms are most common.
Did you know?The direction of the sail along the float determines which way the by-the-wind-sailor will travel. If the sail runs north-west to south-east along the float it will drift left of the wind direction, if the sail runs south-west to north-east it will drift right of the wind direction!
How people can help
Report any sightings of by-the-wind-sailors to your local Wildlife Trust. Look but don't touch – as they may give a mild sting. The Wildlife Trusts are working with sea users, scientists, politicians and local people towards a vision of 'Living Seas', where marine wildlife thrives.