5 distinct coasts, each with different waves, weather, and water quality.
The Hawaii Department of Health recommends staying out of the ocean for at least 72 hours after heavy rain. Oʻahuʻs water quality varies dramatically by coast. The dry leeward side (Ko Olina) has the fewest advisories. The windward side (Kailua) gets the most rain. The North Shore has multiple active advisories.
Character: Tourist center. Waikiki, Ala Moana, Diamond Head. Calm summer surf, moderate winter south swells.
Water quality: Ala Wai Canal is the main contamination source. Eastern end (Kaimana) is cleaner than western end (Fort DeRussy). Moderate rainfall (~20 in/yr).
Key beaches: Waikiki, Ala Moana, Diamond Head
Character: Dry, sunny. Fewest tourists outside Ko Olina. Local communities.
Water quality: Low rainfall = fewest advisories. Ko Olina lagoons are man-made and self-cleaning. Electric Beach (Kahe Point) has warm water discharge from a power plant.
Key beaches: Ko Olina Lagoons, Electric Beach, Makaha Beach
Character: World-famous surf coast. Deadly winter waves (15-30+ ft). Calm summer swimming. Haleiwa surf town.
Water quality: Multiple active advisories (12+ days). More rainfall and agricultural runoff than south shore.
Key beaches: Waimea Bay, Sunset Beach, Pipeline, Sharkʻs Cove
Character: Green, lush, residential. Best beaches on the island (Kailua, Lanikai, Waimanalo). Fewer tourists.
Water quality: More rain (~50 in/yr). Kawainui Marsh drains into north end of Kailua Beach. Kaneohe Bay is murky and not ideal for swimming.
Key beaches: Kailua Beach, Lanikai, Waimanalo
Character: Residential suburb with pocket beaches. Hanauma Bay (famous snorkeling, requires reservation). Sandy Beach (powerful shorebreak, locals only). Makapuʻu Lighthouse Trail.
Water quality: Hanauma Bay is protected and generally clean. Sandy Beach has good flushing.
Key beaches: Hanauma Bay, Sandy Beach, Makapuʻu
Top-rated experiences in the area.
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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. Water quality ratings are estimates based on publicly available testing data and geographic analysis. They are not real-time measurements and may not reflect current conditions.
Always verify current water quality conditions with the Hawaii DOH Clean Water Branch before entering the water.
When in doubt, don't go out. 🤙