Water quality status and bacteria risk rating
📍 Hawaii Kai, Oʻahu — Water sports hub near Hanauma Bay
Maunalua Bay is a large, partially enclosed bay on Oʻahu's East Shore between Hanauma Bay and Hawaii Kai. The bay encompasses the Hawaii Kai Marina and several beach parks including Kuliouou Beach Park and Maunalua Bay Beach Park. Water quality is generally good, with some concerns related to boat fuel and urban runoff from the surrounding Hawaii Kai community.
The DOH monitors portions of the bay periodically. Results are generally within acceptable limits on dry days. The bay's semi-enclosed nature means water circulation is not as strong as open-ocean beaches, which can concentrate any pollutants that enter. The surrounding residential development and the marina contribute to occasional elevated bacteria counts after rain events.
For the best water quality in this area, Hanauma Bay (just east) is the premier choice, though it requires advance reservations and has a daily visitor cap. Maunalua Bay is a great alternative for water sports, kayaking, and casual swimming when Hanauma reservations are unavailable.
Based on: DOH East O'ahu monitoring, marina proximity, semi-enclosed bay circulation, urban runoff from Hawaii Kai
The DOH recommends staying out of the ocean for at least 72 hours after heavy rain. Maunalua Bay can accumulate runoff from the Hawaii Kai watershed. Wait for the water to clear before swimming, and avoid areas near storm drains.
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⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with the Hawaii Department of Health. Water quality ratings are estimates based on available data. They are not real-time measurements.
Always verify with the Hawaii Department of Health Clean Water Branch before entering the water.
When in doubt, don't go out. 🤙