Swimmers and sunbathers arriving at Humiston Park Beach in Vero Beach, Florida got a disgusting surprise last Wednesday evening when they found a mysterious mile-long trail of large feces in the sand.

“I’ve never seen anything like it, and I’ve lived along beaches all my life,” onlooker Bill Becker told TCPalm. “It was disgusting, but mystifying. It looked like Great Dane poop all along the beach.”

Officials with the county’s Environmental Health Department were able to rule out humans as the source of the mess on arrival at the beach, but it took a bit more digging to determine the actual culprit.

“We did a feel and smell test, and based on the description we gave to Florida Fish and Wildlife, they told us it was manatee droppings,” environmental health specialist Charles Vogt said. “I’ve never followed a manatee closely enough to know otherwise.”

Not that a big group of manatees came ashore to use the beaches as their own personal open-air privy. The excrement was washed onto the shore, probably stirred up from the ocean floor by strong winds.

A couple hours of poop scooping took care of the problem and the beach was reopened by the following afternoon.