The so-called super moon over the Florida Keys Saturday night looked great but caused extreme tides, both high and low.
"The high tides are higher and the low tides are lower when the moon is at its closest point to the earth," said meteorologist Alan Futterman from the Key West office of the National Weather Service.
The moon always affects ocean tides but more so at full moon.
A perigee moon -- when a full moon occurs at the closest point to Earth in its elliptical orbit -- increases the apparent size of the moon, and also has a greater effect on tides.
Tides Saturday night and early Sunday swamped some low-lying roads in the Keys. Twelve hours later, the reverse effect drained water off low-lying flats.
Boats trying to take traditional shortcuts through shallow areas sometimes ran aground.
Acres of Atlantic Ocean flats near offshore Tavernier Key, about two miles from the main Keys, allowed strollers to look for shells and dogs to frolic in the soft mud. Pelicans and gulls feasted on fish stranded in shallow pools.
The Florida Keys Mosquito Control District pays close attention to extreme tides, said Executive Director Michael Doyle.
"A lot of offshore islands essentially look like a dinner plate, with a shallow area surrounded by a berm," Doyle said. "Some of these can be hundreds of acres."
In dry periods on the islands, "billions of mosquito eggs lie waiting on the ground," he said. "After a high tide, they begin hatching within hours. This is a major producer of mosquitoes."
The district's offshore crews are allowed to treat most islands with a particular pesticide.
"A 3.5-foot high tide topped with 1.7 inches of rain on Middle Torch will likely cause areas that don't typically retain water to retain water long enough to hatch a brood of mosquitoes," Lower Keys mosquito inspector Yvonne Wielhouwer said.
A perigee moon -- astronomers hate the "super moon" moniker -- are relatively common. However, this summer and fall will see two more, on Aug. 10 and Sept. 19.