Marine Animal Bites or Stings

Written by Teresa Bergen
Medically Reviewed by George Krucik, MD

Marine Animal Bite and Sting Health Risks

Many marine animals bite or sting. Some deliver venom through their teeth, tentacles, spines, or skin. Others, such as sharks, aren’t venomous but can inflict serious bites with their large, sharp teeth. Most creatures that sting or bite have developed these behaviors as defense mechanisms or to help them hunt for food.

Most marine animal stings and bites are caused by accidental contact. For example, you could step on a stingray buried in the sand or brush against a jellyfish while swimming. Divers and fishermen are especially at risk because of their frequent and prolonged contact with marine life.

After any marine bite or sting, seek medical help immediately if you experience:

  • difficulty breathing
  • difficulty remaining conscious
  • chest pain
  • swelling around the sting site
  • vomiting
  • spasms
  • shock
  • severe bleeding

Risks from Marine Animals

Oceans are vast and contain too many creatures with stingers or sharp teeth to list. However, a few creatures have particularly frequent and/or dangerous interactions with humans. Many of these live in warm, shallow water where swimmers and snorkelers are likely to encounter them.

Stingrays

Stingrays have venomous spines on their tails. If you accidentally step on a stingray, it will respond by thrusting its tail into your leg or foot. Venom and spine fragments can cause the wound to become infected.

Stingray stings usually cause intense pain, nausea, weakness, and fainting. In rare cases, the victim might have trouble breathing or even die.

Tentacled Marine

Jellyfish, anemones, and corals all have tentacles. Each tentacle is covered with individual stingers called nematocysts. Jellyfish fire their venomous stingers into prey and sometimes into the legs of swimmers.

Most stings from jellyfish, anemones, and corals cause rashes and sometimes blisters. You might also experience headaches, chest pain, muscle pain, sweating, or a runny nose. Stings from the Australian box jellyfish and the Portuguese man-of-war (found in most warm seas) can be deadly.

California Cones

California cones are snails that have a venom-injecting tooth. When a person picks up a cone, it responds by poking its tooth into the offender.

Reactions include swelling, numbness, blurred vision, respiratory failure, and occasionally, cardiac arrest.

Blue-Ringed Octopus

The blue-ringed octopus of Australia is one of the most dangerous marine animals. Its venomous saliva contains a neurotoxin that leads to respiratory failure and paralysis. When agitated, its blue rings pulsate, signaling that a bite is coming. According to the University of Sydney, one blue-ringed octopus has enough venom to paralyze 10 adult humans.

Sea Urchins

Sea urchins are covered in sharp spines coated with venom. If you step on an urchin, the spines will probably break off and lodge in your foot, producing a painful wound. If the spines aren’t removed completely, the wound can become inflamed, leading to a rash and muscle and joint pain.

Dangerous Large Fish

Large fish, such as sharks and barracudas, can inflict sizeable bite wounds or even dismember or kill humans.

Preventing Marine Animal Bites or Stings

Fortunately, you can take precautions to make your trip to the beach safer.

Be aware.

The best way to protect yourself is to stay out of the way of marine life. When you go to the beach, read any posted warning signs about jellyfish or other dangerous marine life in the area.

Stay away from fishing boats and stay out of the water if you are bleeding; blood can attract sharks from up to a mile away. If you see a shark, leave the water as quickly and calmly as possible.

Shuffle, don’t step.

If you’re walking in shallow water, shuffling your feet can help you avoid stepping directly on an animal. The animal might also feel you coming and get out of the way.

Don’t touch marine animals.

This includes pieces of them—even if they’re dead. A lone tentacle can still be dangerous.

Stay covered.

Clothing can help protect you against stings from creatures and scratches from coral. Chemicals on your skin can trigger jellyfish to release their stingers. Even something as sheer as pantyhose or a special type of sunscreen can form a barrier between your skin chemicals and the jellyfish. Wearing shoes in the water is also a good idea. However, keep in mind that many spiny creatures can cut through a shoe or wetsuit.

Be careful where you put your hands.

A venomous creature might be lurking under a rock or in a crevice.

Treatment for Marine Animal Bites or Stings

Treatments vary depending on the type of bite or sting. But, a few general rules apply:

  • Don’t let the victim exercise, because this can spread the poison.
  • Unless a doctor orders it, don’t administer any medications.
  • Fresh water often aggravates the venom, so rinse wounds only with seawater.
  • If you’re removing a stinger, wear gloves.
  • Use a towel to wipe off stray tentacles or stingers.

Some stings and bites respond well to first aid treatment. A lifeguard can provide first aid, should you need it.

Stingrays

If you can see fragments of the stinger just under your skin, pour salt water over the wound to flush them out. If a spine is embedded in your chest, neck, or stomach, leave removal to the medical professionals. Apply direct pressure if the wound is bleeding heavily. You might need a tetanus shot, antibiotics, and/or stitches. A doctor might also recommend elevating the affected body part for a few days.

Jellyfish

After flushing the sting with salt water, remove tentacle pieces with tweezers or gloved fingers. Vinegar will stop the continued release of venom from a box jellyfish tentacle, but will make a man-of-war sting worse. If you aren’t sure what stung you, seek professional medical treatment instead of treating the wound yourself.

Sea Urchins

Vinegar is also helpful for sea urchin injuries because it dissolves their spines. If the spines have penetrated deep into your skin, a doctor might need to remove them. Soaking the affected body part in hot water helps to relieve pain.

Long-Term Outlook

While a few marine animal bites and stings can be deadly — especially from the blue-ringed octopus or the box jellyfish — most of these injuries are not life threatening. The quicker you get medical care, the faster your stings and bites are likely to heal.

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