Anyone currently wishing to swim on the beaches of the Arcachon Bay or on the Atlantic coast of Gironde often first looks carefully at the sea. In recent days, reports of exceptionally large jellyfish near the coast have been increasing. Some holidaymakers therefore refrain from swimming, while others prefer to 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 open Atlantic to the coast. The interaction of wind, tides and ocean currents is responsible for this. Especially after long periods of westerly winds, the animals drift towards the beach 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 further reinforces this effect. A calm sea and relatively warm surface waters mean that jellyfish remain near the coast for longer. Instead of quickly returning to the open sea, they often stay near the beaches for several days. This is precisely why they are currently attracting the attention of holidaymakers.
The high temperatures of recent weeks have probably also contributed. Many jellyfish species develop more quickly in warmer water, and favorable conditions encourage their proliferation. However, marine biologists have 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.
Why do jellyfish nevertheless cause so much concern? It is above all their size that impresses. Some specimens reach a bell diameter of several dozen centimeters, accompanied by long tentacles that seem to stretch endlessly through the water. Encountering such an animal while swimming quickly inspires respect — which is entirely understandable.
But large does not automatically mean dangerous. Some common species cause only mild skin irritation, while others sting much more painfully. That is why lifeguards generally advise against touching jellyfish — neither in the water nor on the beach. Even animals washed ashore often still have active stinging cells and can cause painful injuries. The rule is clear: do not touch.
Despite the many sightings, most beaches do not have swimming bans. Local rescue services are monitoring the situation closely and inform visitors if large shoals of jellyfish drift near the shore. Anyone wishing to swim should nevertheless remain cautious. It is usually easy to avoid jellyfish, children deserve special attention, and after a sting it is advisable to rinse the affected area with seawater. If symptoms persist or worsen, consulting a doctor provides reassurance.
Jellyfish blooms have always been part of the Atlantic’s natural rhythm and occur regularly, especially between June and August. They may be noticed all the more this summer because many people visit the beaches and sightings are shared on social media within minutes. Who does not know that?
There is therefore no reason for holidaymakers to interrupt their beach stay. With a little attention and by keeping a respectful distance from marine animals, there is generally nothing to prevent enjoying a day by the Atlantic. Often, the wind direction changes after just a few days—and with it, the jellyfish disappear from the swimming areas.