A young bottlenose dolphin has taken up residence in the waters of the French beach town of Saint-Jean-de-Luz, delighting locals and tourists while raising concerns about the animal's safety.

The female cetacean has been lingering just off the southwestern town's central beach since mid-October.

On a recent morning, with the heat already intense and the beach crowded, a dolphin's fin was seen regularly rising above the water just a few meters from the shore, weaving among the swimmers.

Pascale Fossecave, an oceanographer and the city's deputy for environmental affairs who has been observing the animal, said she had apparently been expelled from her pod.

The dolphin has been seeking "social interaction", readily approaching the shore and displaying a marked "curiosity toward humans", Fossecave said.