News 12 New Jersey has previously reported on beaches at the Jersey Shore which have been closed to swimming due to high bacteria levels.

High bacteria levels are typically found after a heavy rainstorm due to runoff from sewer lines.

New Jersey’s beaches are tested weekly by the county health department to make sure they are safe for beachgoers.

"It's our job at the Ocean County Health Department to make sure your water is safe to swim in and when they're not we are going to tell you about it so you can make sure you make the right decision on whether or not to go swimming,” says environmental health coordinator John Protonentis.

Testers will head out into chest-deep water and take a sample from below the surface. Conditions such as air and water temperatures, time of day and location are recorded. The samples are placed in a cooler and brought to a lab at the Ocean County Public Utilities complex in Bayville.

“We will take the sample, bring it into the lab, filter a measured amount of the sample and put it in an agar, which is a nutrient for the bacteria to grow,” says lab supervisor Nora Byrne.

If samples show bacterial levels above the allowed safe levels, swimming is off limits until samples come back clean.

Health officials say it is good practice to not swim in rivers or bays following a heavy rainfall for at least a day or two. They says that this is especially true if the rain happens after the Monday weekly testing period.

A list of all the water testing sites around the state can be found at the New Jersey Department of Environmental Protection website.