The type and species of potentially dangerous or harmful marine life will vary based on the locations and seasons. Of course, your Scuba Diving Instructor will never take you in areas with known dangers without fully briefing you. Nonetheless, below are a few very basic rules:


There are many different species of jelly fish. While most of them are completely harmless, some jelly fish will sting you when in contact with your skin. The best defense is to wear a protection suit. In cold and temperate waters, this is not an issue as you will always wear a full wet suit or dry suit. In tropical waters, an option is simply to wear a skin suit.


Contacts with corals may sometimes cause a rash or allergic reaction. In order to prevent any occurrence, you should always control your buoyancy and simply avoid contact with corals. Not only will this protect you, but it will also prevent damages on a very fragile eco-system.


These fish are venimous and are camouflaged to look like rocks or reefs. Again, the best defense is simply to control buoyancy in order to avoid any contact with the bottom, rocks, reefs or corals. This will ensure you do not have a very unpleasant encounter, while protecting the underwater world from human-caused damage.


Eels may appear scary and somewhat aggressive. Unless you shove your hand right into their pits however, they are all show and are usually completely harmless. Simply watch your animal from a comfortable distance and do not harass it.


Many species of sharks are completely harmless. The aggressive species usually see underwater divers as other predators and will leave them alone. In waters known to be roamed by sharks, spear fishing should be avoided, as the blood and commotion of the killing has been known to attract sharks. In the event of a shark encounter, one should always remain calm and avoid any sudden move. A basic rule that applies to any wildlife encounter.