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  • Writer's pictureScuba Steve

What is a Brown Water Advisory, and Why Should I Care?

A guide for navigating brown water advisories for scuba divers and freedivers in Hawaii

Brown water discharge into the ocean

Hawaii's mesmerizing underwater landscapes attract scuba divers and freedivers from around the world, offering a unique and diverse marine experience. However, the tropical paradise is not without its challenges, and one issue that divers need to be aware of is the occurrence of brown water advisories. In this comprehensive guide, we will delve into what brown water advisories are, why they occur, and why they are crucial for the safety of divers exploring the Hawaiian waters.

Understanding Brown Water Advisories

Brown water advisories are public warnings issued by the Hawaii Department of Health when there is an increased risk of waterborne contaminants in coastal areas. "Brown water" refers to runoff that can contain harmful micro-organisms (pathogens) and other harmful pollutants. This water is often discolored, caused by heavy rainfall and subsequent runoff, carrying sediments, debris, and potential pollutants into the ocean. However, even if water looks clear and blue from the shore, bacteria and debris may still be present in the water.

The primary purpose of brown water advisories is to safeguard public health by notifying individuals, including scuba divers and freedivers, about the potential risks associated with entering contaminated waters. These advisories aim to prevent waterborne illnesses and other health issues that can arise from exposure to polluted coastal areas.  The runoff can contain contaminants from overflowing sewage systems, animal feces, and other chemicals, and it's certainly something you don't want to be swimming in!

Factors Leading to Brown Water Advisories

Heavy rainfall is the number one cause of brown water advisories. Looking at the map above, you can see how intense rainfall over the mountain areas will wash directly downstream into the oceans around the island. Hawaii's tropical climate is prone to sudden and intense rainfalls, causing flash flooding along streams, rivers, and other low-lying areas. The water will carry any nearby soil, pesticides, debris and other nasty pollutants into Hawaii's coastal waters. Some sources of contamination include:

  • Agricultural Practices: The islands of Hawaii have a significant agricultural presence, and the use of fertilizers and pesticides in farming can contribute to water contamination. When rainwater washes these substances into water bodies, it can lead to brown water conditions.

  • Urban Runoff: Urbanization and development contribute to impervious surfaces such as roads and buildings, preventing water from being absorbed into the ground. This runoff can carry pollutants like oil, chemicals, and debris into the ocean, affecting water quality. The Ala Wai Canal is the perfect example of this.

  • Storm Drains: Have you ever seen the "Drains to Ocean" warnings on storm drains? During heavy rainfall, any pollutants running off from urban areas into storm drains can potentially end up in the ocean.

  • Ground Pollutants: Any type of pollutants that are near sources of water can potentially be carried downstream to the ocean. This includes debris, trash, and animal waste. Animal waste is especially concerning for ocean wildlife.

Risks for Scuba Divers and Freedivers

Brown water can present risks for anyone entering the ocean, including scuba divers and freedivers. Divers may be at an even greater risk than most given their prolonged immersion under water.

  • Reduced Visibility: One of the immediate impacts of brown water is reduced visibility underwater. For scuba divers and freedivers, this poses a significant safety concern as it limits their ability to navigate and identify potential hazards.

  • Waterborne Pathogens: Contaminated water may harbor harmful bacteria, viruses, and parasites that can cause waterborne illnesses. Divers need to be cautious about ingesting or coming into contact with such water to avoid health risks. Ingesting brown water can cause serious illness, and exposing open wounds can cause infection.

  • Impact on Marine Life: Brown water events can adversely affect marine ecosystems, leading to the displacement or stress of marine life. Divers should be mindful of the environmental impact and strive to minimize their footprint during these conditions.

Responding to Brown Water Advisories

Stay Informed: Being informed about current conditions is crucial for making safe and responsible decisions. The best way to check for water advisories is on the Hawaii Department of Health Clean Water Branch System. You can subscribe to receive notifications when a beach advisory, beach notification, brown water advisory, sewage spill or permit exceedance is issued, or any water quality advisory is canceled.

Divers should regularly check local weather forecasts and brown water advisories before planning any underwater activities. In the presence of a brown water advisory, divers should consider postponing or canceling their dives to minimize risks to their health and safety. Additionally, some other hygiene practices to consider:

  • Post-Dive Shower: Rinsing in fresh water after diving is great to remove saltwater from your gear and body, but it won't do anything to remove harmful bacteria. Take a proper shower at home with soap after diving, and consider periodically disinfecting your dive gear. Remember, outdoor showers at dive sites often drain to the ocean, so do not use soap at these locations.

  • Clean Your Ears: Your ears can be a frequent site of infection, leading to swimmers ear or ear infections. The main symptoms are ear pain, warmth and itching in the ear canal and inflammation/redness on the external part of the ear. If left untreated, swelling can increase to include nearby lymph nodes and produce enough pain that movement of the jaw may become uncomfortable or painful. To prevent this, rinse your ears with freshwater after diving and consider using over-the-counter disinfect products (EarShield, Swim-EAR, DiverDrops, etc). You can also use a homemade cure by mixing a solution of half rubbing alcohol and half vinegar. The alcohol combines with water in the ear and evaporates removing the water, while the acidity of the vinegar keeps bacteria from growing.

  • Take Care of Wounds: Anyone who spends time exploring the great outdoors (including divers) is going to earn some scrapes and scratches along the way. Any open wound can become a entry-point for bacteria, so be sure to take care of them! Cover open wounds with waterproof bandages, and immediately disinfect and wounds when exiting the water.

  • Rethink the Rinse Bucket: Rinse tanks on boats or in your garage can quickly becoming a breeding ground for bacteria if not properly disinfected. Divers can spread infectious diseases (like conjunctivitis) via mask buckets, so if you've been diving in potentially contaminated water, be sure to disinfect your gear before sharing any rinse buckets.


As scuba divers and freedivers embark on their underwater adventures in Hawaii, understanding and respecting brown water advisories is paramount. By staying informed, recognizing the factors that contribute to these advisories, and taking appropriate precautions, divers can contribute to their safety and the preservation of Hawaii's stunning marine environment. Brown water advisories serve as a reminder that, in the pursuit of exploration, responsible and informed decisions are crucial for the well-being of both divers and the delicate ecosystems they admire.


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