Measuring up to 20 feet (6 m) in length and weighing up to 1,650 pounds (730 kg), the Nile crocodile is one big lizard. These relics of the dinosaur age are patient creatures and can spend up to two hours holding their breath underwater, if they don't move around too much. A typical dive is usually 10 to 15 minutes, though. This ability to stay underwater for extended periods of time is due to the Nile crocodile's very slow metabolism and its efficient allocation of oxygen.
Fortunately for all concerned, crocodiles are predators of opportunity, meaning they are much more likely to lie in wait for a tasty wildebeest to happen by than they are to chase something down. Unfortunately, they are also indiscriminate eaters, which means they find humans as delicious as zebras, hence the large number of human deaths by crocodiles -- about 200 each year. Nile crocodiles are found in rivers and mangroves all over sub-Sarahan Africa, for anyone interested in getting a look at (or avoiding) these dangerous predators.
Interesting facts about crocodiles: