Anyone wishing to enter the water on the beaches of the Bassin d’Arcachon or the Atlantic coast of Gironde during this period often first takes a careful look at the sea. In recent days, reports of unusually large jellyfish near the coast have increased. Some holidaymakers therefore decide not to swim, while others observe these fascinating animals from the beach. The sight is impressive, but in most cases it is a completely normal natural phenomenon.
During the summer months, jellyfish regularly arrive from the Atlantic Ocean towards the coast. The interaction of wind, tides and ocean currents is responsible. Especially after prolonged periods of westerly winds, the animals are pushed towards the shore and gather in sheltered bays or shallow coastal areas. Around Arcachon, this spectacle can be observed almost every year — sometimes more intensely, sometimes less so.
The current weather situation amplifies this effect. Calm seas and relatively warm surface waters mean that the jellyfish remain close to the coast for longer. Instead of being quickly pushed back out to the open sea, they often stay near the beach for several days. This is precisely why holidaymakers notice them particularly these days.
The high temperatures of recent weeks are probably also contributing. Many jellyfish species grow faster in warmer waters, and favorable conditions promote their reproduction. Nevertheless, marine biologists see no reason to attribute every jellyfish-rich year solely to climate change. Populations naturally fluctuate significantly. Currents, food availability, and reproductive success also play a decisive role.
But why do jellyfish cause so much unease? Above all, their size is impressive. Some specimens reach a bell diameter of several dozen centimeters, accompanied by long tentacles that seem to stretch endlessly through the water. Anyone who encounters such an animal while swimming immediately feels respect — and that is entirely understandable.
But large does not automatically mean dangerous. Some of the most common species cause only mild skin irritation, while others sting much more painfully. Therefore, lifeguards generally advise against touching jellyfish — neither in the water nor on the beach. Even stranded animals often still retain active stinging cells and can cause painful injuries. One clear rule applies: do not touch them.
Despite numerous reports, there are no swimming bans on most beaches. Local lifeguard services are monitoring the situation closely and inform visitors if large swarms of jellyfish approach the shore. However, anyone wishing to swim should remain cautious. Jellyfish can usually be avoided without difficulty; children deserve special attention, and after a sting it is advisable to rinse the affected area with seawater. If symptoms persist or are more severe, a medical check-up provides reassurance.
Jellyfish blooms have always been part of the natural rhythm of the Atlantic and occur regularly, especially between June and August. Perhaps they are also more visible this year because there are many people on the beaches at the same time and sightings are shared on social media within minutes. Who has not experienced this?
There is therefore no reason for holidaymakers to interrupt their seaside holiday. With a little care and by keeping a respectful distance from marine animals, a day on the Atlantic is usually not at risk. Often the wind direction changes after just a few days — and with it, the jellyfish disappear from swimming areas.