Swimmers are going to want to stay away from the waters of the lagoon inside DuBois Park in Jupiter on Wednesday.
Health officials said people could get sick if they go into the water.
Crews aren't sure what the exact cause of the bacteria is but say it could be from local wildlife or rain runoff.
The county will test the waters again on Thursday to see if the bacteria has gone down.
While the lagoon has the high levels of bacteria, the county says the ocean is safe for people to swim in.
This is the fifth time this year that the park has had to be closed due to high bacteria levels.