Cobia

The cobia is a relatively unknown fish. When most people come across it they think it is a shark. That is because after they are born, cobias tend to leave their mothers to live with a pod of sharks. For a time they foloow their new family, copying their moves. When they are old enough, cobias leave the sharks to live on their own. They make other animals that would be their predators believe that they are actually sharks so they get left alone. The main difference between cobias and sharks are that cobias are bony fish. Unlike the shark they have an actual skeleton made from bones.

Kemp's Ridely Sea Turtles

While there are many different species of sea turtles in the Carribbean, I figured I talk about the Kemp's Ridley. Kemp's Ridely's are not only the smallest of all sea turtles but they are also the most endangered. The reason for this is because they only nest on specific beaches in Mexico. Those beaches are being populated by humans. When they are born, hatchlings need to get themselves into the water straight away or else they won't make it. To find the water, they use the moon light to guide them. However, human development has added street lights to the mix and the hatchlings can get confused.
Turtles are a cold blooded species. Like most reptiles they grow according to how much they eat. Their diets are primarly vegetarian so there is plenty of food for them. During the summers they migrate up North as far as New England. The main problem with that is when it gets cold and they start their trip South, some get caught in the arm of Cape Cod. If they don't get out before the water temperatures drop they come down with what is called cold stunning. Cold Stunning is when they can't move their limbs and they come down with hypotherma and frost bite. Since they can't swim they wash up on the shore where volunteers for local aquariums rescue them and tehy are rehabilitated. The New England Aquarium in Boston has a large turtle rescue recovery program during the winter.

SHARKS!!!!!

I figured I'd start with probably the most popular marine animal. Sharks are fish, but instead of bones inside of them, they are made out of cartilage. Humans have cartilage on the tips of our noses and the tops of our ears. Most people are afraid of sharks since movies (Jaws) portray them as viscous man-eating creatures. Most species however tend to avoid people. In the Caribbean there are a few different species of sharks that divers are more likely to see.

Nurse Shark

One of the most popular, and probably the coolest shark in my opinion is the nurse shark. Nurse sharks, unlike most other sharks, live on the bottom of the ocean. They don't need to swim in order for water to pass over their gills. Instead they can stay stationary and pump water through a device called a spiracle. Nurse sharks look a lot like catfish. But unlike catfish they can grow to over ten feet in length. Their bodies are a purple color and when they swim, which is not often, they have a yellow tint around them. Living on the bottom they tend to eat bottom dwellers. The barbels on the front of their face can detect creatures under the sand, which helps them find food. Unless they are bothered, they leave humans completely alone. However, if a human does something stupid like pull their tail, they'll bite the human and not let go. It's just better if you don't bug them.
  The Caribbean Reef Shark is another common shark found in the tropics. They look like what most humans classify as sharks. So long as they are in an open area  with plenty of ocean to swim in, they won't go near humans. They give birth to live young between November and December. Another shark like them are sand tiger sharks.  Since both species must keep swimming in order for water to pass over their gills, they have the ability to shut down half their brain at the time so that they can rest it.
Shark teeth are very common to find on a beach. Since their skeleton is made up of cartilage, there is no hard jaw for teeth to stick to. Instead teeth tend to fall out when a shark eats. To compensate for that, sharks have rows and rows of teeth in the back that move forward everything they loose one.
In short, if you see a shark while diving, that's really cool. Keep your distance and watch it swim, but don't try to get in the way.

Intro to the Tropical Ecosystem

The waters of the Caribbean hold some of the most interesting places to dive. Besides the warmth of the water, there are plenty of coral reefs and ship wreck to explore. What you'll find at those dive spots are hundreds of different species of marine life.
Coral Reefs are found in over 100 countries and cover about 109,800 sq miles. That is less than .01% of the ocean's floor. However, they are one of the most productive ecosystems in the world. I could go into the science behind the reason for this great biodiversity, however this blog is about diving. 
 My posts will be about the kind of animals you will see and the background on them. Everything on a coral reef has its place. You have the best chance of finding bony fish, cartilaginous fish, crustaceans, cephalopods, reptiles, and mammals. There are plenty of other groups, but these tend to be the more interesting creatures. I could spend time talking about porifera (sponges) and echinoderms (sea stars, urchins, sea cucumbers, sea biscuits) but for the amount of time I have, I'm going to focus on the other groups.
DBN