If you're looking for a place to cool off on the Treasure Coast, avoid the North Fork of the St. Lucie River.
Swimming is not recommended and the advisory will be in place for at least another week after the health department found high levels of an intestinal bacteria in the water last Friday.
Scientists say the problem is heavy rains causing storm runoff.
Zack Robertson has already noticed it.
"It's got this dirty nasty hue," says Robertson.
Most recent testing labels the water quality as poor.
"One of the major problems," says Brian Lapointe with FAU Harbor Branch.
He has been studying this issue for more than 30 years.
"Poor soil conditions and int he wet season, high water cables that in many cases infiltrate the drains fields of septic tanks," says Lapointe.
He says he is working on a study with Port St. Lucie city leaders to find the source of the pollution.
The department of health plans to sample the water next Monday.