Contact Irritation

• Avoid contact with sea urchins and other poisonous marine life.Sea Urchin image by vi from Fotolia.com
  
  Sometimes simply coming in contact with a poisonous or venomous sea creature is enough to injure or even kill a person. Jellyfish are notorious for their venom, and the box jellyfish is one of the most deadly of all. Known to have killed humans on numerous occasions, these creatures have tentacles about 5 meters long that contain millions of stinging cells known as nematocysts. Portuguese man-of-war, sea wasps, sea anemones, sea cucumbers, stinging corals, crown-of-thorns starfish, hydroids, irukandji and sea urchins are other types of venomous or poisonous marine creatures humans should avoid.
  
  

Ingested Toxins

• Never consume pufferfish or other poisonous fish.Puffer Fish image by Freelance from Fotolia.com
  
  Some kinds of fish and sea creatures are not meant for human consumption. Others seem fine to eat for some people (scallops, oysters and other shellfish) yet cause an allergic reaction in others. Pufferfish are well-known sea creatures that are poisonous to eat, often with fatal results. Porcupine fish, cowfish, boxfish, tobies and sunfish also have toxin in their bodies.
  
  

Injected Toxins

• Some sea creatures inject their toxins into their prey.southern stingray 3 image by Christian Schoettler from Fotolia.com
  
  Certain marine creatures are capable of injecting venom or toxins into their prey --- as well as into humans. While beautiful, divers and other swimmers should avoid contact with cone shells, which have a remarkable amount of venom. One geographer cone (Conus geographus) contains enough venom to kill roughly 700 people. Other sea creatures that may inject toxins include the blue-ringed octopus, stingrays, stonefish, sea snakes and a variety of venomous fish.
  
  

Other Dangerous Sea Creatures

• Respect the ocean and its many inhabitants and use caution when exploring underwater environments.shark image by krotex from Fotolia.com
  
  Not all dangerous sea creatures use venom or poison when attacking their prey. Sharks, for instance, are one of the most well-known sea predators and attack a number of humans every year. Other significant marine predators include the barracuda, moray eels, large grouper and saltwater crocodile. It is best to explore unfamiliar waters in the company of an experienced guide whenever possible to avoid dangers.