Water quality status and bacteria risk rating
📍 In Honolulu between Waikiki and downtown, next to the Ala Moana Shopping Center
Hawaii's busiest beach park with roughly 4 million visitors per year. A long, reef-protected stretch of sand between Waikiki and downtown Honolulu. The park includes Magic Island, a man-made peninsula with a calm lagoon. Popular with locals for after-work swimming, picnics, and outrigger canoe paddling. The Ala Wai Canal and Kewalo Basin are the primary contamination concerns after rain.
Ala Moana Beach Park is Hawaii's busiest beach, drawing an estimated 4 million visitors per year. It is a DOH Tier 1 beach, meaning it gets tested at least weekly due to high use and multiple risk factors. The beach has a documented history of bacteria exceedances, including a reading of 1,013 enterococci per 100mL in January 2018 — nearly 8 times the EPA recreational swimming threshold of 130 CFU/100mL.
Several factors converge here: the Ala Wai Canal outlet nearby discharges urban runoff from Honolulu's watersheds, storm drains along the park carry street-level pollutants, and a breakwater limits water circulation in the swimming area. DOH notes that the sheer number of bathers itself increases bacteria risk.
Based on: DOH Tier 1 beach, advisory history (Jan 2018, Oct 2018, Sep 2019, Feb 2025), Hawaii Business Magazine reporting on DOH beach monitoring
Ala Moana Beach Park stretches nearly a mile along the south shore. Water quality varies by location because of where the contamination sources are and how the reef traps water.
Closest to the Ala Wai Canal outlet and boat harbor. After rain, contaminated runoff from the canal reaches this area first. The enclosed lagoon at Magic Island has limited flushing. Surfrider testing has found elevated bacteria here after storms.
The main swimming area protected by an offshore reef. The reef creates calm, shallow water ideal for families but also limits ocean flushing — contaminants take longer to clear here than at open beaches. Multiple storm drains along the park discharge directly into this zone.
The western end near Kewalo Basin. Slightly better circulation than the central area because the reef opens up toward the basin. Still receives storm drain runoff but less exposure to Ala Wai Canal discharge.
Ala Moana's offshore reef creates the calm, shallow swimming conditions that make it popular for families. But that same reef limits ocean circulation. At open beaches, waves and currents flush contaminants out within hours. At Ala Moana, the reef-protected lagoon exchanges water more slowly, meaning bacteria and pollutants persist longer after rain events.
This is the key difference between Ala Moana and an open beach like Waikiki — the same rainfall event can produce elevated bacteria levels at Ala Moana that last 1-2 days longer than at Waikiki. The DOH website does not explain this distinction.
Lower rainfall reduces Ala Wai Canal and storm drain discharge. Water quality generally passes DOH testing. High bather load in summer can still elevate bacteria. Best conditions early morning before crowds.
Heavy rain events flush the Ala Wai Canal watershed into the ocean. DOH advisories are most common during this period. The reef-protected lagoon clears slowly. South swells in summer can also push contaminated water from the harbor area toward the beach.
The 72-hour rule is especially important at Ala Moana. After heavy rain, the Ala Wai Canal flushes contaminated runoff from Honolulu's central valleys directly into the ocean near this beach. Storm drains throughout the park also carry pollutants. Even if the water looks clear, bacteria can remain elevated for days. Stay out of the water if the Ala Wai looks brown or turbid where it meets the harbor near Magic Island.
The Ala Wai Canal is one of Hawaii's most polluted waterways. Built in 1928 to drain the wetlands that became Waikiki, it now channels runoff from the Manoa, Palolo, and Makiki valleys through central Honolulu and out into the ocean near the Ala Wai Boat Harbor — right next to Magic Island at the Diamond Head end of Ala Moana Beach Park.
Researchers at the University of Hawaii have documented toxic levels of Vibrio vulnificus (a flesh-eating bacterium) in the canal. In 2006, a major sewage line break forced the city to dump 48 million gallons of untreated sewage into the canal, closing nearby beaches for a week. Over 11,000 cesspools on O'ahu, many in the Ala Wai watershed, continue to leach human waste into groundwater and eventually the canal.
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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.
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