It’s safe to go back in the water again. That was the word on Seth’s Pond from the West Tisbury health agent John Powers Thursday afternoon, one day after the freshwater pond was 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 enterococcus bacteria. The pond closed three times in June, then again for six weeks in July and August. On August 9, Mr. Powers said he had five clean water 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 was able to re-open the pond.

But after less than a week with swimmers back in the water, Mr. Powers was forced to close the pond again yesterday when samples taken Monday again showed high levels of bacteria. A water sample taken Wednesday showed the pond was now clean.

Rainwater is known to spike bacteria levels.

Mr. Powers also has said the shallow depth of the pond during the dry summer could be affecting bacteria levels.

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.