Hawaii Ocean Water Quality

If you Google "Hawaii water quality," almost every result is about tap water — drinking water regulations, pipe safety, that kind of thing. That’s not what this page is about.

This is about the ocean. Specifically: is the water at your beach safe to swim in right now? Hawaii’s tap water is generally fine. The ocean is a different story — it depends on the beach, the weather, and what’s upstream.

Hawaii has roughly 83,000 cesspools — more than any other US state. These are basically holes in the ground where untreated sewage goes. The waste seeps into groundwater and eventually reaches the ocean. The worst example is Kahaluʻu Beach Park on the Big Island, where UH researchers confirmed a cesspool sewage plume reaching the ocean through the lava rock. In January 2026, bacteria there hit 2,005 per 100mL — fifteen times the safe limit.

When it rains hard, everything on the ground — dirt, animal waste, fertilizers, garbage, overflowing cesspool and sewer waste — gets washed into the ocean. This triggers brown water advisories. The water turns brown or murky and can stay contaminated for days. The DOH says wait 48-72 hours after rain before getting in.

Brown water advisories happen regularly — there are active ones right now from this past weekend’s storms.

Beaches near river mouths get hit the hardest. The rivers collect everything from the entire watershed — agricultural chemicals, residential waste, eroded soil — and dump it right where people swim. Hanalei Bay on Kauai is the textbook example: the Hanalei River empties directly onto one of the most famous beaches in Hawaii, and Kauai’s north shore is one of the wettest places on Earth.

We have water quality pages for Hawaii’s biggest resorts. Each one shows the bacteria risk at your hotel’s beach, live advisories, and nearby alternatives.