The most dramatic water quality gap of any resort comparison in Hawaii. Hanalei Bay has been federally impaired since 2004. But Poipu has a hidden hotspot tourists need to know about.
Poipu’s open-ocean beaches are dramatically cleaner than Hanalei Bay. Hanalei Bay and all four of its feeder streams have been classified as impaired for enterococcus bacteria by the Hawaii DOH since 2004. In 2024, the Hanalei River failed every single Surfrider water quality test.
Important caveat: Waikomo Stream at Koloa Landing — a popular snorkeling entry point within the Poipu resort area — had a 90% bacteria failure rate in 2024 and made Surfrider’s national hotspot list. The open-ocean beaches at Poipu test clean. The stream mouth does not.
Hanalei Bay is one of the most spectacular bays in Hawaii — and one of the most polluted. The Hawaii DOH has listed some combination of Hanalei Bay and its four feeder streams as impaired for enterococcus bacteria in every biennial report since 2004.
The bay receives discharge from the Hanalei River, Wai’oli Stream, Waipa Stream, and Waikoko Stream — all classified as impaired. The Hanalei Initiative has mapped over 360 active cesspools from Hanalei to Ha’ena, with roughly 150 still operating in the town area alone. Many cesspools have been upgraded to septic systems in recent years, which has helped, but the bay remains impaired.
In 2024, three Kaua’i BWTF sites failed every single water test: Hanalei River at Weke Road, Hanamaulu Stream Mouth, and Nawiliwili Stream. The eastern end of Hanalei Bay near Black Pot Beach (where the river enters) is consistently the worst. During wet weather, the Hanalei River has recorded readings as high as 6,867 enterococci per 100mL — more than 50 times the safe limit.
The western end of the bay, near Waikoko and the 1 Hotel, tends to be cleaner — but the entire bay is influenced by the same watershed and is classified as impaired.
Source: EPA Hanalei Bay Watershed page; Hawaii DOH 2020 Integrated Report; Surfrider Kaua’i BWTF 2024; The Garden Island (Feb 2023); Hanalei Initiative
Poipu’s open-ocean beaches sit on Kaua’i’s drier south shore and benefit from strong ocean circulation and fewer stream inputs than the North Shore. Surfrider testing consistently shows the Waiohai surf break (fronting the Grand Hyatt and Sheraton area) measuring low for bacteria. Salt Pond Beach Park on the west side also tests clean.
The exception is Waikomo Stream at Koloa Landing. This is a popular entry point for shore diving and snorkeling within the Poipu resort area. In 2024, 90% of water samples at this site exceeded state health standards, earning it a spot on Surfrider’s national Beach Bacteria Hot Spots list alongside Kahalu’u on O’ahu. The contamination comes from the stream — cesspools and land-based runoff in the Koloa area feed into Waikomo Stream.
The critical distinction: Poipu Beach Park and the resort hotel beaches test clean. Koloa Landing does not. They are separate locations within the same general resort area, roughly a 5-minute drive apart. Tourists should know the difference.
Source: Surfrider Kaua’i BWTF 2024; Surfrider 2024 National Clean Water Report; The Garden Island (various)
In 2024, the Kaua’i BWTF conducted a landmark study testing 24 streams across the island for both enterococcus and sucralose — an artificial sweetener that passes through the human body and cesspools unaltered, serving as a definitive marker of human sewage. All 24 streams tested exceeded state bacteria standards, and sucralose was detected in 79% of streams tested. In 14 streams, sucralose was found in at least half of samples, confirming chronic human sewage contamination.
This study is significant because it distinguishes human sewage from animal waste — a question that enterococcus testing alone cannot answer. The presence of sucralose proves that Kaua’i’s cesspools are actively contaminating coastal waters.
Source: Surfrider 2024 Hawaii Water Quality Report; peer-reviewed study in PMC (Berg et al.)
Book Poipu. The south shore offers the cleanest resort swimming on Kaua’i. Stick to Poipu Beach Park and the open-ocean beaches. Avoid Koloa Landing / Waikomo Stream mouth.
Hanalei Bay is stunning and the experience may be worth the trade-off for many travelers. But know the risks:
• Swim on the western end of the bay (toward Waikoko), away from the river mouth at Black Pot.
• Never swim after rain. The bay’s four feeder streams flush cesspools and agricultural runoff directly into the water. 72-hour rule →
• Keep children out of the river mouth area. Surfrider has noted that kids are often seen wading at Black Pot with parents unaware of contamination.
• Rinse thoroughly after swimming — eyes, ears, nose, mouth. If you have open wounds, don’t enter the water.
If you’re staying at the Marriott Kauai Beach Club at Kalapaki Bay, be aware that Nawiliwili Stream has failed 100% of Surfrider water tests since 2016. The average bacteria count was 1,004 MPN in 2024. A permanent warning sign was posted at the stream mouth in 2024. The open bay is cleaner than the stream mouth, but caution is warranted after rain.
Hawaii DOH Clean Water Branch — 303(d) impaired waters list; beach monitoring. eha-cloud.doh.hawaii.gov
Surfrider Kaua’i — BWTF 2024, sucralose stream study, 18 monthly sites. kauai.surfrider.org
EPA Region 9 — Hanalei Bay Watershed, TMDLs. epa.gov
Hanalei Initiative — Cesspool mapping, water quality advocacy. hanaleiinitiative.org
The Garden Island — BWTF reporting (Feb 2023, Mar 2023, Oct 2024).
⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with any government agency or monitoring organization. Assessments are based on publicly available data. They are not real-time measurements. “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.
Always verify current conditions with the Hawaii DOH Clean Water Branch before entering the water.
When in doubt, don’t go out. 🤙