Advisories are informational only. Beaches remain open. The decision is yours.
This guide is for general informational purposes only. Always verify current conditions and consult healthcare professionals for medical concerns.
This guide provides essential information about water quality conditions relevant to this topic in Hawaiʻi. The state's 88,000 cesspools, steep volcanic terrain, and intense tropical rainfall create unique water quality challenges that differ significantly from mainland beach conditions.
The most important thing visitors need to know is the 72-hour rain rule: avoid ocean swimming for at least 72 hours after significant rainfall. During this period, stormwater runoff carries bacteria from cesspools, animal waste, and urban contamination into streams and the ocean. Check current advisory status on Safe to Swim Hawaii before every beach visit.
Water quality in Hawaiʻi varies dramatically by location and weather. Some beaches on dry, leeward coastlines have excellent water quality that rivals the cleanest beaches anywhere. Others near stream mouths, canal outlets, and cesspool-dense areas have chronic contamination challenges. The difference between a clean swim and a health risk often comes down to checking conditions before getting in.
Hawaiʻi's 88,000 cesspools release approximately 53 million gallons of untreated sewage into the ground daily. This sewage travels through porous volcanic rock to the coast, contaminating groundwater and nearshore ocean water. Some coastal cesspools are less than 500 feet from the shoreline. The 2050 cesspool conversion deadline (Act 125, passed 2017) requires all cesspools to be upgraded, but progress has been slow due to costs averaging $20,000-$60,000 per property.
The DOH Clean Water Branch monitors approximately 100 beach sites for Enterococcus bacteria. When levels exceed 130 CFU/100mL, a beach advisory is issued. However, not all beaches are monitored, testing frequency varies, and brown water advisories are issued without lab testing. This means actual bacteria levels during the worst conditions are often unknown. Safe to Swim Hawaii aggregates data from DOH, USGS stream monitoring, NOAA ocean conditions, and NWS weather alerts to provide a more complete picture.
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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 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.
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. 🤙
Safe to Swim Hawaii checks water quality data every 15 minutes from multiple government agencies. When conditions change — a new advisory is posted, stream levels spike after rain, or an advisory is cancelled — our pages update automatically. This means you are seeing the latest available data from official sources, not a static snapshot.
The Hawaii Department of Health Clean Water Branch operates the state’s official beach monitoring program. Tier 1 beaches are tested weekly; Tier 2 beaches are tested less frequently. When bacteria levels exceed 130 enterococci per 100 mL, the DOH issues a Beach Advisory for that location. Brown Water Advisories are issued based on visual assessment of runoff conditions, not bacteria testing.
USGS stream monitoring stations measure water flow (discharge) and turbidity in real time. When a stream near a beach is flowing at 5x or more above its normal rate, this indicates significant runoff that likely carries elevated bacteria. We display these stream conditions alongside DOH advisories to give a more complete picture of water quality at each beach.
The Hawaii Department of Health tests Tier 1 beaches (the most popular ones) weekly and Tier 2 beaches less frequently. However, most of Hawaii's 300+ swimmable beaches have no regular testing program at all.
Brown water is caused by heavy rainfall washing soil, debris, and contaminants from land into the ocean through streams and storm drains. The discolored water can contain elevated bacteria, pesticides, and sewage overflow. The DOH recommends staying out of brown water for 48-72 hours after rain stops.
The general guideline is to wait at least 72 hours after heavy rain before swimming. Beaches near stream mouths and urban areas carry higher risk. Open ocean beaches on dry coasts recover faster. Always check for brown or murky water before entering, regardless of advisory status.
Tier 1 beaches are tested weekly. Tier 2 less frequently. Most of Hawaii's 300+ beaches have no regular testing.
Enterococci is a type of bacteria used as an indicator of fecal contamination in ocean water. The DOH threshold is 130 CFU per 100 mL. Levels above this trigger a Beach Advisory.
Yes. Swimming in water with elevated bacteria can cause skin rashes, ear infections, stomach illness, and eye infections. People with open wounds or weakened immune systems are at higher risk. Consult a doctor if you develop symptoms after ocean exposure.
When an advisory is cancelled, the DOH has determined conditions have improved. However, water quality can vary by location within a beach area. If the water still looks discolored or murky, use your own judgment and consider waiting longer.