Every major Kauaʻi hotel mapped to its actual beach with water quality data
Top-rated experiences near this beach. Check water quality, then plan your trip.
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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.
Safe to Swim Hawaii aggregates water quality data from six independent sources to provide broader coverage than any single agency. Our sources include the Hawaii Department of Health Clean Water Branch (beach advisories and bacteria testing), USGS National Water Information System (25 stream monitoring stations across all islands), NOAA CO-OPS (tide levels and water temperature), NDBC (wave buoys and ocean conditions), NWS Honolulu (weather and marine alerts), and City & County of Honolulu Environmental Services (Kailua Bay water testing and spill reports).
Historical bacteria risk ratings on this site are based on DOH testing data, Surfrider Foundation monitoring, geographic analysis (stream proximity, cesspool contamination areas, coastal development), and advisory frequency. These are historical assessments, not live measurements. Always check the live advisory status at the top of each page and verify conditions with the Hawaii DOH Clean Water Branch before entering the water.
Less rainfall means less runoff and generally cleaner ocean water across all islands. Stream flows drop, reducing bacteria transport to coastal areas. This is typically the best time for ocean water quality, though localized contamination from cesspools and urban runoff can still occur.
Frequent heavy rain events cause stream flooding, sewage overflows, and brown water advisories. Windward and north-facing coasts receive more rain. The DOH issues the most advisories during this period. Leeward coasts (west-facing) generally stay drier and cleaner year-round.
Water quality patterns vary significantly by location. Beaches near stream mouths and urban areas show the most dramatic seasonal variation. Open ocean beaches with strong wave action maintain better water quality year-round. Check individual beach pages for location-specific seasonal data.
Hawaii has approximately 88,000 cesspools — more than any other U.S. state. These underground chambers collect untreated household sewage and allow it to leach into the surrounding soil and groundwater. In coastal areas, this contaminated groundwater eventually reaches the ocean through submarine groundwater discharge, contributing to elevated bacteria levels at nearby beaches.
Hawaii Act 125 (2017) requires all cesspools to be upgraded or converted to approved septic systems by 2050. Priority areas near the coast and drinking water sources are being addressed first, but progress has been slow. Beaches in known cesspool contamination zones carry elevated bacteria risk even during dry weather. For more information, see our comprehensive cesspool guide.
⚠️ 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 data. They are not real-time measurements.
Always verify conditions with the Hawaii DOH Clean Water Branch before entering the water.
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. 🤙