A sudden and unusual retreat of the sea was seen at Arenal beach yesterday, Monday, 24 August.
The water was pulling noticeably away from the shoreline and temporarily exposing part of the seabed. A strong current was also noticed flowing out through the Fontana Canal towards the sea.
The phenomenon is possibly a rissaga, or meteotsunami, although this has not been officially confirmed by AEMET.
A meteotsunami is a sudden change in sea level caused by atmospheric conditions rather than an earthquake. Rapid changes in atmospheric pressure, often associated with storms or unstable weather, can create waves that travel across the sea. When these waves reach shallow or enclosed coastal areas, the water can suddenly withdraw from the shore and then return, sometimes quite dramatically.
Similar effects were reportedly noticed elsewhere along the Marina Alta coast.
The phenomenon can be unsettling, but the sudden withdrawal of the water does not necessarily mean a conventional tsunami is approaching. Nevertheless, anyone on the beach who notices an unusually rapid or significant change in sea level should move away from the shoreline and follow any instructions from the authorities.
Another unusual sign reported during the event was that one person noticed his hair suddenly standing on end. This can occur when a strong electrical field develops in the atmosphere, often associated with storm activity. While it does not by itself confirm an imminent lightning strike, it is considered a warning sign to take thunderstorms seriously and move to a safe, enclosed location.