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

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


Stingrays have venomous spines on their tails. If you accidentally step on a stingray, it may 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, a person who is stung might have trouble breathing or even die.

Tentacled marine life

Jellyfish, anemones, and corals all have tentacles. Each tentacle is covered with individual stingers called nematocysts. Jellyfish generally fire their venomous stingers into prey, but sometimes they come into contact with swimmers.

Most stings from jellyfish, anemones, and corals cause rashes and sometimes blisters. You may also experience:

  • headaches
  • chest pain
  • muscle pain
  • sweating
  • runny nose

Stings from the Australian box jellyfish and the Portuguese man-of-war, found in most warm seas, can be fatal.

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, and respiratory failure. In rare instances, a person may experience cardiac arrest.

Blue-ringed octopus

The blue-ringed octopusof 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 along with muscle and joint pain.

Dangerous large fish

Large fish, such as sharks and barracudas, can inflict sizeable bite wounds. Although such bites are rare, these fish can dismember or even kill humans.

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

  • Don’t exercise, because it can spread the venom more quickly.
  • Unless a doctor orders it, don’t administer any medications.
  • Rinse wounds only with seawater, unless advised otherwise by medical personnel.
  • If you’re removing a stinger or tentacles, wear gloves.
  • Avoid elevating the affected area of the body.

For most stings and bites, a lifeguard can provide first aid.

However, you should be prepared in case a lifeguard isn’t available. Here are some basic first aid tips for treating stings from three common culprits.


After flushing the sting with salt water, remove tentacle pieces with tweezers or gloved fingers. In the past, vinegar was often used to rinse the affected area. However, vinegar is no longer recommended since it may activate stinging cells that haven’t fired yet. Instead, once all tentacles have been removed, apply an ice pack to reduce inflammation and pain. Never urinate on a jellyfish sting.

Most jellyfish stings are minor and require only basic first aid. But some stings can be serious or even fatal. If you experience chest pain, difficulty breathing, or if a large area of your body was stung, seek medical help immediately.

Sea urchins

Use sterile tweezers to remove any spines that are visible in the wound. If the spines have penetrated deep into your skin, a doctor may need to remove them. Soaking the affected body part in hot water helps to relieve pain. Use water that is as hot as you can tolerate. Take care to test the water to make sure it isn’t hot enough to cause burns.

You can also take over-the-counter pain relievers. If you notice signs of an allergic reaction, such as difficulty breathing or chest pain, seek emergency medical help.


If you are stung by a stingray, call an ambulance immediately. If a spine is embedded in your skin, it’s generally best to leave removal to medical professionals. You can rinse the area with salt water to remove any sand or debris. Usually, the sting is very painful. Standard first-aid treatment includes immersing the affected area in water that is as hot as can be tolerated. Take care to check the water temperature first.

At the hospital, your doctor will clean the wound and examine the area for damage. You might need a tetanus shot, antibiotics, or stitches. Your doctor can also recommend or prescribe medication to relieve the pain.

You can take precautions to make your trip to the beach safer. If you’re on vacation or visiting a beach for the first time, always check to find out what types of marine life are in the area.

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.

Stay away from fishing boats and stay out of the water if you’re 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

Don’t touch any marine animals, even if they are dead. This includes pieces of them. 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 some creatures have spines that can pierce a shoe or wetsuit.

Be careful where you put your hands

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

Most marine animal bites and stings are not life-threatening. For minor stings, you may be able to treat yourself with basic first aid and over-the-counter medication. Even so, it’s a good idea to play it safe. Don’t hesitate to seek medical help if a sting seems to be serious. If you have symptoms like difficulty breathing or swallowing, chest pain, or paralysis, seek emergency medical care right away.