Waterborne Illnesses

What Divers Need to Know

The underwater world is full of fascinating creatures. Most are harmless, but some microbes found in the diving environment can cause health issues for divers, especially divers with an immunodeficiency or open wound. Elevated concentrations of microbes are also possible in communal rinse tanks. The bacteria found in these rinse tanks can infect even the healthiest divers. Fortunately, it’s easy to avoid contracting and spreading unwanted illnesses by taking the right precautions.

Microorganisms in the Mask Bucket

A rinse tank can quickly become a breeding ground for bacteria, so divers who have been exposed to contagious illnesses should avoid washing their gear in water shared by others. In March 2006, 27 divers visited a site and 13 of them contracted conjunctivitis, also known as pink eye, which can have a viral or bacterial source. Two physicians later concluded the outbreak originated with a local divemaster. Not coincidentally, all of the divers who rinsed their masks in the communal tank contracted conjunctivitis, while those who rinsed their masks elsewhere remained uninfected.

Vibrio Bacteria and Vibrosis

Vibrio bacteria inhabit warm, brackish water and can cause an illness known as vibriosis. Symptoms of vibriosis include abdominal cramps, diarrhea, fever, headache, nausea and vomiting. In most cases, symptoms resolve in two to three days, but hospitalization may be required for severe cases.

Most people contract vibriosis by eating raw or partially cooked fish or shellfish; however, divers have an increased risk of exposure to Vibrio bacteria through water. The pathogen can enter the body via swallowed water or through the ears, open wounds or the mucus membranes of the eyes, mouth or nose.

Vibrio bacteria flourish in areas exposed to sewage or runoff from large human or animal populations. Divers with weakened immune systems should avoid diving in these areas. According to the Centers for Disease Control and Prevention (CDC):

  • About 80 percent of vibriosis infections occur between May and October when water temperatures are warmer.
  • Vibriosis causes 80,000 illnesses each year in the United States. Consumption of contaminated shellfish is the suspected cause in about 50,000 of these cases.
  • Symptoms usually appear 12-24 hours after consumption, but onset can take as long as four days.

Open Wounds and Skin Infections

Divers with an open wound, even a small cut or scrape, are at risk for a skin infection caused by Mycobacterium marinum. The infection first appears as a red or tan skin bump (granuloma) or a string of small, reddish bumps (Sporotrichotic lymphangitis). Because Mycobacterium marinum is slow-growing, the condition may take weeks to develop. Treatment typically includes a course of oral antibiotics.


Even the clearest, most beautiful tropical waters are home to numerous microbes. Bacteria in salt water, fresh water and rinse tanks can cause problems for divers regardless of their health status. To avoid infection, divers with compromised immune systems or open wounds should refrain from scuba diving until their bodies are fully healed. Other ways to stay healthy include:

  • Avoid using communal equipment rinse tanks.
  • Clean dive gear using disinfectants under running water.
  • Never dive with open wounds (including recent tooth extractions).
  • Do not dive if you are sick or have an infection.
  • Wash any wounds incurred while diving thoroughly with soap and water.
  • Wear appropriate exposure suits to protect your skin from cuts and scrapes underwater.

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