It's only the moon, emergency officials in Puerto Rico are telling nervous islanders who have feared that recent extreme tides portend a tsunami or biblical catastrophe.
Waters receded up to 50 feet this week during low tide on Puerto Rico's southern coast, sparking a flurry of calls to seismology and geological agencies from people worried about natural disasters or supernatural events. Tsunamis are sometimes preceded by a dramatic drop in sea level.
"There are people who have said it's a biblical sign," said Pedro Calixto, who lives in the southern coastal town of Guayama. "There are others who don't dare go into the ocean because they believe it's a supernatural thing."
Severe tide changes occur a couple of times a year worldwide, and are happening now because the moon is at its closest point to earth, said government seismologist Alberto Lopez Venegas. The closer the moon is, the stronger its gravitational pull on water.
About 75 people have called Puerto Rico's seismological agency this week, including one woman who refused to believe the scientific explanation, said data analyst Harold Irizarry.
"She could not be convinced," he said.
People in the southern coastal town of Ponce have been seen walking over areas normally covered by water, studying exposed rocks, coral and sea shells.
Puerto Rican geologist Gisela Baez said officials are reminding residents that there have been no earthquakes to generate a tsunami.
The extreme-tide phenomenon has been noted across the Caribbean and in Central America.
Some beaches along the Pacific coast of El Salvador have seen tides that are 10 feet (3 meters) lower than usual, said Francisco Gavidia, oceanography director with El Salvador's Department of Natural Resources.
"We have received calls because people are a bit scared," he said.
Tides across the globe are affected, but the change is more noticeable on shallow beaches, experts say.