Data-driven rankings based on DOH bacteria testing, geographic exposure, and contamination sources.
The Big Island's Kohala/Kona coast (west side) receives only 10-20 inches of rain per year, while the Hilo side gets over 100 inches. For the most reliable water quality, the west side is dramatically better. Always follow the 72-hour rain rule regardless of which side you visit.
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The 72-hour rule is the standard guideline from the Hawaii Department of Health: avoid swimming for at least 72 hours after heavy rain stops, especially near stream mouths, canal outlets, and areas with brown or discolored water. This applies to all beaches across all islands.
Bacteria from urban runoff, agricultural land, and aging cesspool systems enters the ocean through streams and storm drains. Hawaii has approximately 88,000 cesspools — more than any other state — many of which leak untreated sewage into groundwater that eventually reaches the coast. Beaches near known cesspool contamination areas carry higher risk, particularly after rainfall.
⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project. Rankings are estimates based on publicly available data, not real-time measurements.
Always verify conditions with the Hawaii DOH Clean Water Branch.
This site does not recommend or advise anyone to swim at any beach. We share government data and geographic analysis so you can make your own informed decisions. By using this site you accept full responsibility for your own safety. See our Terms of Use for full details.
When in doubt, don't go out. 🤙