A lot of the beaches here have cabins which contain lifeguards: Salvamento en playas. All cabins are made of wood. Some are blue, others are red and yellow, like this one.
The cabins carry a flag. The flags are like traffic lights. Varying the swimming conditions the flags are red, orange, or green. Green is safe. The rest you can guess yourselves.
The cabins contain one or two ultra young men who wear very dark sunglasses, look tedious and sit on a chair that tips backward on two legs. The cabin on this beach was about as big as the beach. This probably explains why the young salvavidas didn’t bother to look outside. Although the green flag might also have done the trick.