Why It Matters for Your Swim
The Ala Wai Canal is a man-made waterway built in the 1920s to drain the wetlands that are now Waikiki. It collects water from three stream systems and the entire Honolulu urban watershed, carrying it to the ocean near the Hilton Hawaiian Village.
The canal carries urban runoff, bacteria from thousands of upstream cesspools, and pollutants into the nearshore ocean. After heavy rain, bacteria levels in the canal spike dramatically and the contaminated water spreads along the Waikiki shoreline.
The DOH recommends staying out of the ocean near the canal mouth, especially after rain. On dry days, ocean currents help disperse pollutants. After storms, the 72-hour rain rule applies to all of Waikiki, particularly the western end closest to the canal.
The Hawaii Department of Health recommends staying out of the ocean for at least 72 hours after heavy rain, even if the water looks clear. Bacteria and pollutants from runoff can linger in the water longer than the brown color does.
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⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — it is not affiliated with the Hawaii Department of Health, O'ahu beaches, or any government agency or hotel brand. Water quality ratings on this site are estimates based on publicly available testing data and geographic analysis. They are not real-time measurements and may not reflect current conditions. “No DOH Alerts” means no advisory is currently posted — it does not mean the water was tested and found safe. DOH only monitors a fraction of Hawaii’s beaches, and some areas have no regular testing at all.
Always verify current water quality conditions with the Hawaii Department of Health Clean Water Branch before entering the water. This site is for informational purposes only and should not be the sole basis for any swimming decisions.
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When in doubt, don’t go out. 🤙