Key Biscayne water quality today

What the readings mean

DOH-Miami-Dade reports sampling 16 county beach sites weekly through the Florida Healthy Beaches Program. It tests for Enterococcus, an indicator bacteria associated with fecal pollution. The state says possible sources include stormwater runoff, pets and wildlife, and human sewage. Results are reported in colony-forming units (CFU) per 100 milliliters of marine water.

The current Florida DOH categories are:

• Good — 0 to 35 CFU/100mL.
• Moderate — 36 to 70 CFU/100mL.
• Poor — 71 or more CFU/100mL.

A category describes one sample. It does not account for changes since that sample, and a Poor result is not the same thing as a formal advisory.

What an "advisory" actually means

A formal advisory means DOH recommends against water-related activity at that location because of an increased risk of illness. Florida's program says an initial result above 70 CFU/100mL is re-sampled; if the re-sample also exceeds 70, an advisory is issued. DOH-Miami-Dade keeps the advisory in place until follow-up testing is below the accepted health level.

The advisory applies to the named sampling location. Crandon Park North, Crandon Park South, and Cape Florida are reported separately, so compare the row for the beach you plan to visit.

A recent Crandon North example

On May 22, 2026, DOH-Miami-Dade issued a water-quality advisory for Crandon Park North after testing found bacteria above the accepted level. It advised against water-related activity at that location.

On May 28, the county lifted the advisory after a May 27 test showed an acceptable level. That is why the sample date and the latest county notice both matter.

What causes high readings

Enterococci live in the intestinal tracts of people and animals. Florida DOH says their presence can indicate fecal pollution from sources such as:

• Stormwater runoff
• Pet and wildlife waste
• Human sewage

High concentrations may indicate that other organisms capable of causing illness, infections, or rashes are present. The bacteria count is an indicator; it does not identify the specific pollution source.

Where to swim when there's an advisory

If DOH lists an advisory, avoid water-related activity at the named location. Compare the separately reported rows for Crandon North, Crandon South, and Cape Florida, but check each sample date before choosing an alternative. A recent Good result elsewhere is useful context, not a guarantee of current conditions.

Water-quality testing also does not cover surf, currents, or marine-life hazards. Check the beach flag for those conditions. If seaweed is your concern, use the separate Key Biscayne sargassum report.

Source

This page checks the Florida Department of Health beach-water-quality dashboard every 30 minutes and groups the published counts using DOH's categories. Official sampling is periodic, and DOH-Miami-Dade notices may report an advisory change before the dashboard updates.