Went swimming in brown water, murky runoff, or water during an active advisory? Do not panic, but do not ignore it either. This guide covers exactly what to do right now, what symptoms to watch for over the next 72 hours, and when you should see a doctor.
The single most important thing you can do after swimming in contaminated water is to shower with soap and clean water as soon as possible. The faster you rinse off, the lower your risk of developing an infection. Bacteria from contaminated ocean water can enter your body through your mouth, nose, ears, eyes, and any break in the skin — even tiny cuts you might not notice.
Shower thoroughly with soap. Use antibacterial soap if you have it. Scrub your entire body, paying special attention to your armpits, groin, and any area where skin folds trap moisture. Contaminated water residue on your skin can cause rashes and infection even hours later.
Flush your ears. Tilt your head to drain water from each ear, then gently rinse with clean fresh water. Swimmer’s ear (otitis externa) is one of the most common infections from contaminated water and develops when bacteria get trapped in the ear canal. A 50/50 mix of white vinegar and rubbing alcohol as ear drops after swimming helps prevent infection by restoring the ear canal’s acidity.
Rinse your eyes and nose. If you opened your eyes underwater or got splashed in the face, rinse both with clean fresh water. Flush your nose gently — bacteria can enter through nasal passages and cause sinus infections.
Clean any open wounds immediately. This is critical. If you had any cuts, scrapes, reef cuts, or abrasions while in contaminated water, wash the wound thoroughly with soap and clean water, apply an antiseptic like hydrogen peroxide or povidone-iodine, and cover with a clean bandage. Wound infections from contaminated ocean water can escalate quickly, especially in Hawaii’s warm, humid climate.
Wash your swimsuit separately. Do not just rinse it and hang it up. Wash it with detergent in hot water. Bacteria can survive on wet fabric for hours.
If you swallowed water: Drink plenty of clean water over the next few hours. This dilutes anything you ingested and keeps you hydrated if gastrointestinal symptoms develop later. Do not induce vomiting — it does not help and can cause additional problems.
Different infections have different incubation periods. Most people who develop symptoms after swimming in contaminated water will notice something within the first 72 hours. Here is what to monitor and when.
Eye irritation: Redness, stinging, or watery eyes. Usually mild and resolves with rinsing. If it persists past 24 hours or includes discharge, it may be bacterial conjunctivitis.
Skin irritation: Itching, redness, or a prickly sensation, especially in areas where contaminated water sat against your skin (under swimsuit, skin folds). This is often a chemical or bacterial irritant reaction and may resolve with showering. Watch for it progressing to raised bumps or blisters.
Nausea: If you swallowed contaminated water, mild nausea can begin within hours. Stay hydrated. If it escalates to vomiting, see the 4–24 hour window below.
Gastroenteritis: This is the most common illness from contaminated water. Symptoms include stomach cramps, nausea, vomiting, and watery diarrhea. Most cases are caused by enterococcus, E. coli, or norovirus from sewage runoff. Mild cases resolve in 1–3 days with rest and hydration. See a doctor if vomiting or diarrhea is severe, bloody, or lasts more than 24 hours.
Ear pain (swimmer’s ear): Itching and discomfort in the ear canal, sometimes with muffled hearing. Pain typically worsens when you tug on your earlobe. This is otitis externa — bacterial infection of the outer ear canal. Over-the-counter ear drops can help early cases, but see a doctor if pain is severe or you develop drainage.
Wound redness and swelling: If a cut or scrape that was exposed to contaminated water starts to become red, warm, swollen, or painful, this may be the beginning of a wound infection. Clean and rebandage. If the redness spreads or you develop fever, seek medical care promptly.
Staph / MRSA wound infection: A wound that looked mildly red at 24 hours may now be significantly swollen, painful, warm to the touch, and possibly draining pus. Staph infections, including MRSA, can progress rapidly in Hawaii’s warm climate. If a wound has a spreading red border, streaks radiating outward, or a pus-filled center, see a doctor the same day. Hawaii has among the highest rates of community-acquired MRSA in the United States.
Vibrio wound infection: This is the most serious concern. Vibrio vulnificus is a bacteria that lives in warm brackish water — exactly the conditions found where runoff meets the ocean. Vibrio infections of wounds can progress from mild redness to blistering, tissue breakdown, and life-threatening bloodstream infection within 24–48 hours. Rapidly spreading wound infection with fever, chills, or blistering is a medical emergency.
Ongoing GI symptoms: If diarrhea or vomiting persists past 48 hours, or if you develop fever, bloody stools, or signs of dehydration (dark urine, dizziness, dry mouth), see a doctor. What started as a simple stomach bug may need treatment.
Leptospirosis (freshwater exposure): If you were in a stream, waterfall, river, or pond — not just the ocean — watch for fever, headache, muscle aches (especially calves and lower back), and red eyes 2–14 days after exposure. Leptospirosis is a serious bacterial infection spread through animal urine in freshwater. It can be treated with antibiotics if caught early, but severe cases can cause kidney failure, liver damage, and meningitis. See our leptospirosis guide for more details.
Persistent skin rash: Some bacterial skin infections develop slowly. If you develop a rash, recurring boils, or a slow-healing wound days after ocean exposure, see a doctor and mention your contaminated water exposure. Chronic skin infections sometimes need cultures to identify the correct antibiotic.
Not every exposure to contaminated water leads to illness. Most healthy adults who shower promptly and had no open wounds will be fine. But it helps to know what the actual risks are so you can recognize a problem early.
Cause: Enterococcus, E. coli, norovirus, and other pathogens from sewage runoff. Onset: 4–48 hours. Symptoms: Nausea, vomiting, diarrhea, stomach cramps. Treatment: Usually resolves on its own with rest and fluids in 1–3 days. Seek care if severe, bloody, or lasting more than 24–48 hours. Prevention: Avoid swallowing ocean water, especially within 72 hours of rain.
Cause: Staphylococcus aureus, including drug-resistant MRSA strains. Found in coastal waters after runoff and in beach sand. Onset: 1–3 days. Symptoms: Red, swollen, warm, painful area around a wound. May develop a pus-filled center (abscess) or look like a spider bite. Treatment: Antibiotics, sometimes incision and drainage. MRSA requires specific antibiotics. Why Hawaii is different: Hawaii has consistently reported among the highest rates of community-acquired MRSA in the U.S. The warm climate, outdoor lifestyle, and frequency of minor skin wounds from reef and lava rock create ideal conditions. Read more in our staph infection guide.
Cause: Vibrio vulnificus and Vibrio parahaemolyticus bacteria, naturally present in warm coastal and brackish water. Concentrations increase after runoff events. Onset: 12–72 hours for wound infections, 4–96 hours for gastroenteritis from ingestion. Symptoms (wound): Rapidly spreading redness, blistering, tissue breakdown, fever, and chills. Symptoms (ingestion): Watery diarrhea, cramps, nausea, fever. Treatment: Antibiotics. Severe wound infections may require surgery. Rapidly progressing wound infection is a medical emergency. Risk factors: Open wounds, liver disease, diabetes, immunocompromised status, heavy alcohol use.
Cause: Bacteria (often Pseudomonas aeruginosa) trapped in the ear canal by water. More common in contaminated water. Onset: 12–48 hours. Symptoms: Ear pain (worse when pulling the earlobe), itching, muffled hearing, sometimes drainage. Treatment: Antibiotic ear drops, keeping the ear dry. Prevention: Drain ears after swimming, use drying drops (50/50 vinegar and rubbing alcohol), avoid inserting objects into the ear canal.
Cause: Leptospira bacteria, spread through the urine of infected animals (rats, mongooses, feral pigs, cattle) in freshwater. Relevant when: You were in a stream, waterfall, river, or standing freshwater — not just the ocean. Risk increases dramatically after rain when flooding washes animal waste into waterways. Onset: 2–30 days, typically 5–14 days. Symptoms: High fever, severe headache, muscle aches, red eyes, vomiting. Can progress to kidney failure, liver damage, and meningitis. Treatment: Antibiotics (most effective when started early). Full leptospirosis guide →
Most healthy adults who briefly swam in contaminated water and showered promptly will not develop a serious illness. But certain factors significantly increase your risk.
Any break in the skin is a direct entry point for bacteria. This includes razor cuts, insect bites, reef cuts (extremely common in Hawaii), fresh tattoos, and surgical incisions. Reef cuts are particularly concerning because coral fragments can embed in the wound, creating a persistent bacterial reservoir. If you have any open wound, do not enter the water during or after a rain event, brown water advisory, or any known contamination.
People with weakened immune systems face significantly higher risk of serious infection from contaminated water. This includes people undergoing chemotherapy, organ transplant recipients on immunosuppressive drugs, people with HIV/AIDS, and those taking long-term corticosteroids. For immunocompromised individuals, even brief exposure to contaminated water can result in severe infection. Consult your doctor before ocean swimming in Hawaii, especially during wet season.
People with liver disease (cirrhosis, hepatitis, or other conditions) are at dramatically elevated risk for Vibrio vulnificus infection. According to the CDC, people with liver disease are approximately 80 times more likely to develop Vibrio bloodstream infection and have a much higher fatality rate. This risk factor is important for visitors who may be consuming more alcohol than usual while on vacation.
Young children swallow more water while swimming, have less developed immune systems, and dehydrate faster from gastrointestinal illness. They also tend to have more minor skin wounds. Parents should be especially cautious about letting young children swim after rain events.
Older adults, particularly those with chronic conditions like diabetes, are more susceptible to infections and their complications. Wound healing is slower, immune response may be weaker, and dehydration from gastroenteritis can be more dangerous. If you are over 65, consider avoiding ocean swimming for the full 72 hours after any rain event.
Most contaminated water exposures resolve on their own. But certain symptoms demand medical attention. Hawaii has excellent hospitals on every major island, and urgent care clinics are available in all resort areas.
• A wound develops rapidly spreading redness, blistering, or dark/necrotic tissue
• You develop high fever (above 101°F / 38.3°C) with chills after wound exposure to warm ocean water
• You cannot keep any fluids down for more than 6 hours
• You develop bloody diarrhea or vomit blood
• You feel confused, extremely weak, or have difficulty breathing
• Fever above 100.4°F (38°C) that lasts more than a few hours
• A wound becomes red, swollen, warm, and painful (especially with pus)
• Vomiting or diarrhea that persists more than 24 hours
• Ear pain that worsens or develops drainage
• Eye redness with discharge that does not resolve with rinsing
• You are immunocompromised, have liver disease, or are on chemotherapy and had any contaminated water exposure
Tell them specifically that you swam in potentially contaminated ocean water in Hawaii. Mention the date, whether it was after rain, and whether you had any open wounds. This information helps them consider the right pathogens — particularly Vibrio, MRSA, and marine-specific bacteria that mainland doctors may not immediately think of. If the wound looks like a staph infection, ask them to culture it before starting antibiotics so they can identify MRSA if present.
Now that you know what contaminated water can do, here is how to minimize your risk for the rest of your trip.
Follow the 72-hour rule. Wait at least 72 hours after rain before swimming. This is the single most effective prevention measure. Read our complete guide to swimming after rain for details by beach and island.
Check for advisories before you go. Visit Safe to Swim Hawaii or the Hawaii DOH Clean Water Branch to check for active brown water advisories, beach advisories, and sewage spill notifications.
If the water looks brown, do not go in. No exceptions. Brown water means runoff is actively flowing into the ocean. Even without an official advisory, visual contamination is a reliable indicator.
Cover all wounds with waterproof bandages. Even tiny scrapes and insect bites. Waterproof adhesive bandages are available at any Hawaii pharmacy or ABC Store. Apply them before every ocean swim, not just after rain.
Choose leeward beaches after rain. Leeward (south and west) coasts are drier and have less runoff. Beaches like Hapuna, Wailea, Ko Olina, and Poipu recover fastest because they have no stream outlets and receive less rain.
Avoid swallowing water. This is obvious but worth stating. Keep your mouth closed while swimming and body surfing, especially in areas near stream outlets or storm drains.
Shower immediately after every ocean swim. Not just after contamination events. Making this a habit greatly reduces your lifetime risk of ocean-borne infections.
100+ beaches and 25+ hotels across all islands
Free alerts when water quality changes at your beach — brown water advisories, bacteria warnings, and all-clear notices.
No spam. Just safety alerts for your trip.
⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — it is not affiliated with the Hawaii Department of Health or any government agency. This page provides general information about possible health risks from contaminated water. It is not medical advice. If you are experiencing symptoms after swimming in contaminated water, consult a healthcare professional. Water quality ratings on this site 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 Department of Health Clean Water Branch before entering the water.
When in doubt, don’t go out.