The group were at a popular seawater pool when the wave struck, prompting a major rescue operation

Four people are dead and one is missing after a powerful wave dragged a group of swimmers out to sea while they were in a popular seawater pool along the rocky, western coastline of the Spanish island of Tenerife, Spanish authorities said on Monday.

Crews recovered three bodies on Sunday – a 35-year-old man, a 55-year-old woman and another man about whom no information was given – during a major rescue operation that used jet skis and helicopters to locate and pick up people dragged out to sea. The fourth victim, a woman, died on Monday, a day after being revived at the scene and airlifted to a hospital.

Two of the victims were Romanian and two were Slovaks, their respective governments said. No further information about the identities of the victims was provided.

The pool at Isla Cangrejo, on Tenerife’s Los Gigantes coast, is very popular with foreign tourists, according to local media. Bordered by volcanic rock on one side and walled off from the sea on the other, the pool sits at nearly sea level and can be very dangerous during rough seas when large waves can easily overcome the cement barrier.