Ocean reefs are breathtakingly beautiful places to dive but within the beauty lie many dangers for even the most careful divers. The reefs are a wild habitat. They are not a zoo or an aquarium. They offer an abundance of things to learn, but we must be careful to consider their health first and foremost as they are a vital part of all ecosystems.
Keep in mind that reef creatures have evolved over millions of years into perfect predators specifically designed to catch their favorite prey. These evolutions did not consider mankind. When you enter a reef you are lunging into the middle of a complicated food web that does not take your life into account. Swim carefully. Look but don't touch. Remember above all else that this is their home.
The predators on this list do not have a taste for human flesh. They have venom, stingers, sharp teeth and a will to survive. If you get too close you will likely suffer, but divers are not on their menu and they do not seek purposefully to maim.
Top Ten Dangerous Ocean Reef Predators:
10)Hydroids are anemones and include the stinging fire coral. Fire coral is really not a true coral at all. This anemone is covered with tiny tentacles that will cause irritation and pain. For a fire coral it is mainly protection from predators. Other anemones though, use their stingers to capture and paralyze fish which they then consume. Stings from anemones are painful for divers, but not deadly (http://www.mf.uni-lj.si/acta-apa/acta-apa-01-1/4-clanek.html ).
9) Sting rays are generally docile, but they are defensive. Their barbed stingers contain venom, but it is generally the actual wound that causes all the damage. Wounds from their stingers can easily become infected and in some cases cause death through trauma depending on the placement of the wound (http://www.barrierreefaustralia.com/the-great-barrier-reef/stingrays.htm).
8) Reef Sharks are probably at the top of many lists just because of the bad reputation they have from movies like the infamous Jaws series. However, they do not consider humans specifically as prey. Still, if a diver mimics the behavior of their prey, is spear fishing, or getting too close, they may be provoked to attacked and their sharp teeth can be lethal. (http://www.divingwithsharks.com/shark-info/facts-reefsharks.html)
7) Sea Snakes are highly venomous, true reptiles that breathe air but live their lives in the reefs. Some species do not pack any poison but others have venom twenty times more lethal that that of a cobra. Sea snakes are generally docile, but like any of the reef creatures they will defend themselves with force. If their fangs puncture the skin of a diver, the venom works fairly quickly. It isn't always lethal but it must be treated immediately. As with other venom it can cause cardiac arrest, paralysis and shock (http://www.reef.edu.au/asp_pages/secb.asp?FormNo=54).
6) Eels of some species can grow to be seven or eight feet in length. Though they are not generally aggressive they can become territorial. Because of the sharp teeth and quick strikes that they evolved to catch fish they can do a diver some serious harm (http://www.nativeplanet.org/health/dangeroussealife.htm).
5) Blue-ringed octopuses are small and beautiful. Their venom is especially potent, and helps them to immobilize the crabs they feast upon. When they are not agitated they are yellowish in color but when they are afraid or hunting, brilliant blue rings appear on their entire body. Their strong beaks can nip through a wetsuit no problem, delivering the poison straight to a diver. Like other venomous reef creatures, the blue ringed octopus can be lethal. It can cause paralysis, cardiac arrest and shock (http://www.earlham.edu/~sheedjo/blue-ringedoctopus.htm).
4) Lion fish are strangely beautiful and very hard not to notice. Some lion fish stalk their prey. Using careful steady movements they watch their quarry, then begin rattling their spiny fins just before they gulp down their meal. Lion fish are very poisonous but with caution, easily avoided. (http://www.reefkeeping.com/issues/2002-11/fm/feature/index.php).
3) Stone fish are tiny masters of disguise. Their brownish colors and craggy shape help them to blend into the rocky reefs they inhabit. Their poison is much like that of the lion fish but they are hard to see and therefore harder to avoid (http://www.australianfauna.com/stonefish.php).
2) Box Jellyfish eat small fish and crustaceans. They have very deadly venom that causes pain to anyone that comes in contact. They can also cause death through cardiac arrest and shock. Unlike true jellyfish that drift, box jellyfish are active hunters and can see their prey with advanced eyes located on the sides of their bell. These jellyfish sting to paralyze because they need to immobilize their prey for their own safety as their form is extremely fragile( http://www.outback-australia-travel-secrets.com/box-jellyfish.html).
1) Cone Shell Snails have barbs that they shoot at unsuspecting fish. These barbs earn them their meals, but can also kill a diver. If a cone shell mistakes any part of the diver for a fish and shoots the barb, the diver has got to get to the hospital immediately. The venom is highly potent from these inconspicuous brown shelled snails (http://www.aloha.com/~lifeguards/coneshel.html).