How Florida Tests Beach Water for Bacteria

Every time you see a water quality reading on Safe to Swim Florida, it came from a real water sample collected and analyzed through a state-run program. Here's how the whole process works.

The Healthy Beaches Program

Florida's beach water quality monitoring is run by the Florida Department of Health (DOH) Healthy Beaches Program. County health departments collect water samples at designated monitoring sites across the state. The program has been running since 2000 and covers beaches in most coastal counties.

Not every beach in Florida is monitored — the program focuses on high-traffic public beaches. Smaller, less-visited beaches may not have regular testing data available.

What Bacteria Are They Looking For?

Florida tests saltwater beaches for enterococcus, a group of bacteria found naturally in the intestines of humans and animals. The presence of enterococcus in ocean water is a strong indicator that the water has been contaminated with fecal matter — from sewage overflows, stormwater runoff carrying animal waste, or wildlife.

Enterococcus itself can cause illness, but the real concern is what it signals: where there's fecal contamination, there may also be viruses, parasites, and other pathogens that can make you sick.

How Samples Are Collected

Trained field staff collect water samples following standardized procedures:

1. Location: Samples are taken at designated monitoring points, typically in waist-deep water where people swim.
2. Technique: Sterile collection bottles are submerged about 6 inches below the surface to avoid collecting surface film.
3. Timing: Samples are usually collected in the morning on weekdays. They are not collected during weekends or holidays.
4. Transport: Samples are kept cool and transported to the lab within 6 hours of collection.

How Samples Are Analyzed

In the lab, samples are processed using EPA-approved methods. The most common method is EPA Method 1600 (membrane filtration):

1. A measured volume of water is passed through a membrane filter that traps bacteria.
2. The filter is placed on a growth medium (a nutrient plate that feeds bacteria).
3. The plate is incubated at a specific temperature for 24 hours.
4. Lab technicians count the bacteria colonies that have grown on the filter.

Understanding CFU/100mL

Results are reported as CFU/100mL — Colony-Forming Units per 100 milliliters of water. Each "colony" represents a cluster of bacteria that grew from a single cell or group of cells in the sample.

How Often Are Beaches Tested?

Monitored beaches are tested at least twice per month (bi-weekly). Some popular beaches may be tested weekly. Testing happens year-round but the schedule can be affected by:

• Weather events (tropical storms, hurricanes)
• Holidays and weekends (no sampling)
• Budget and staffing constraints
• County-specific policies

Turnaround Time

From sample collection to results, the process typically takes 24–48 hours. This means the most recent test result on any beach page may not reflect today's actual conditions — it reflects conditions when the sample was taken.

This is one reason we recommend extra caution after rain events: a "Good" reading from last Tuesday doesn't account for a thunderstorm that hit on Thursday. See our guide on swimming after rain.

What About Freshwater?

Florida also tests some freshwater swimming areas (springs, lakes, rivers), but uses E. coli as the indicator bacteria instead of enterococcus. Safe to Swim Florida currently focuses on saltwater ocean beaches. Freshwater sites may be added in the future.

Limitations of Testing

While bacteria testing is the best available indicator of beach water safety, it has limitations:

• Point-in-time snapshots. Results tell you about one moment at one location — conditions change constantly.
• Sampling frequency. Bi-weekly testing can miss short-lived contamination events.
• Not all pathogens detected. Enterococcus is an indicator, not a comprehensive pathogen test.
• Doesn't cover all hazards. Bacteria testing doesn't measure red tide toxins, chemical pollutants, or jellyfish.