Water quality status and bacteria risk rating
📍 Windward Oʻahu near Kualoa Ranch, about 40 min from Waikiki
Kualoa Regional Beach Park has generally good water quality. The Windward coast benefits from trade wind-driven ocean circulation. However, streams from the Koʻolau Mountains drain through nearby valleys and can carry elevated bacteria levels after rainfall.
During dry weather, water quality is typically good. After heavy rain, some stream runoff can temporarily affect the nearshore water. The beach sits on a narrow point of land, which helps with flushing, but the adjacent bay areas can hold runoff longer. Avoid swimming for 72 hours after heavy rain.
Based on: DOH beach monitoring, proximity to stream discharge, Windward coast exposure
At Kualoa Beach, the Department of Health recommends staying out of the ocean for at least 72 hours after heavy rain. Streams from the Koʻolau Mountains can carry elevated bacteria levels into the nearshore water. This is especially important on the Windward side, which receives more rainfall than other parts of Oʻahu. Wait for the water to clear before swimming.
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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 or any government agency. 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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