Update 30 March: Another jellyfish invasion has arrived at Tenerife beaches after the creatures started to arrive en masse this morning at El Médano and Playa de las Vistas, Los Cristianos. By midday, seven bathers had been attended at El Médano alone for stings.
Update 31 January: Jellyfish invaded a swathe of Arona and Adeje coastline yesterday, leaving the beaches of Los Cristianos, Las Vistas, El Camisón and Troya at the mercy of the creatures. Some 11 bathers were treated for stings, and swimmers were again advised to steer clear of the water. It is hoped that a change of wind direction will alter the currents today to steer the creatures away from bathing areas.
I am grateful to Sergio from www.mardefoto.com for permission to use the above photo of jellyfish in the Los Cristianos shallows.
Update 14 January: Today all four beaches in El Médano are closed to swimmers. The La Tejita, Chica, El Médano and Leocadio Machado beaches are all affected by the jellyfish invasion. Nine people have now been treated for stings. The El Cabezo and La Jaquita beaches are not affected.
Original post 13 January: El Médano beach and the neighbouring Leocadio Machado beach are closed to swimmers after being affected by an invasion of jellyfish. The creatures were first spotted yesterday by the hundreds of bathers using the beaches, seven of whom had to be treated for stings. Today, no incidents have been recorded but the beaches remain restricted for swimmers. If anyone is stung while on the beaches themselves, however, there is a help post next to the town beach.