It’s safe to swim in the water — again. That was the word on Seth’s Pond from West Tisbury health agent John Powers Thursday morning, only one day after the freshwater pond had been closed for swimming.

The popular swimming pond off Lambert’s Cove Road has been closed for most of the summer due to high levels of enterococci bacteria, organisms that may indicate the presence of fecal coliform bacteria. Seth’s Pond closed three times throughout June, then again for six weeks in July and August.

However, just in the past week, the pond has been opened, closed and now re-opened again.

On Thursday, August 9, Mr. Powers said he had five clean samples that met the state criteria for a geometric mean of levels at or below 33 colony forming units (CFU) per 100 milliliters of water. And so the pond was opened to swimmers for the first time in more than a month.

But less than a week later on Wednesday, August 15, Mr. Powers once again closed the pond when samples taken on Monday showed high levels of bacteria. Wednesday’s water samples came back with clean results, and so swimmers are welcome once again.

Mr. Powers said the shallow depth of the pond during the dry summer could be affecting bacteria levels, as tests from the deep water came back better than those from shallow water.

“The pond is very low right now,” said Mr. Powers. “That has to do with the amount of rainfall and no snowfall last year. There is nothing recharging it.”

According to the state Department of Public Health, swimming in water with high levels of enterococci can be dangerous for young children, the elderly, and people with compromised immune systems.