What causes them, which islands are most affected, how long they last, and how to check before you swim
A brown water advisory is issued by the Hawaii Department of Health (DOH) when elevated bacteria levels are detected in ocean water near a beach, typically following heavy rain. The "brown water" refers to the discolored, sediment-laden runoff that flows off the land and into the ocean through streams, storm drains, and direct coastal runoff.
Rain picks up bacteria from animal waste, septic systems, agricultural areas, and urban surfaces as it flows toward the coast. Once it enters the ocean, it can spike enterococcus and other bacteria counts to levels that pose a real health risk to swimmers.
Key point: Not every beach is tested after every rain event. Many beaches in Hawaii have no regular monitoring at all. A beach without a posted advisory is not necessarily safe — it may just be untested. Your own eyes are always your last line of defense.
Farms, pastures, and livestock areas contribute bacteria-laden waste that rain washes directly into streams and coastal waters. Common on Kauaʻi, Maui's north shore, and Big Island valleys.
Paved surfaces concentrate runoff rapidly. Storm drains on Oʻahu and Maui funnel contaminants directly to the ocean, often discharging right at popular beaches.
Hawaii has over 80,000 cesspools statewide — more per capita than any other state. Heavy rain can overwhelm these systems, pushing sewage toward the coastline. This is a chronic statewide issue.
When streams flood, they carry everything from their watershed to the ocean. Beaches near stream mouths are consistently the highest-risk spots during and after rain.
Most brown water advisories resolve within 24–72 hours after the rain stops, once ocean currents and wave action flush the affected area. However, several factors can extend an advisory:
Even without a posted advisory, the DOH recommends waiting at least 72 hours after heavy rain before ocean swimming. The water must also visually clear — brown or murky water means conditions haven't recovered even if an advisory was never posted.
Check the DOH: Visit eha-cloud.doh.hawaii.gov/cwb and search for your beach by island and name. Active advisories are shown in red.
Check Safe to Swim Hawaii: We pull the same DOH data and display it on each beach page in real time.
Apply the 72-hour rule: If it rained heavily in the last 3 days, consider waiting regardless of what any advisory says.
Look with your own eyes: Brown, cloudy, or discolored water is the clearest sign. Don't enter if you have any doubt.
Get notified when a brown water advisory is issued or lifted at your island — before you head to the beach.
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⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with the Hawaii Department of Health or any government agency. Information on this page is for educational purposes only and should not be the sole basis for any swimming decisions.
Always verify current conditions with the Hawaii Department of Health Clean Water Branch before entering the water.
When in doubt, don't go out. 🤙