Bull Shark

Initially, scientists thought the sharks in Lake Nicaragua belonged to an endemic species, the Lake Nicaragua shark (Carcharhinus nicaraguensis). In 1961, following specimens comparisons, taxonomists synonymized them. They can jump along the rapids of the San Juan River (which connects Lake Nicaragua and the Caribbean Sea), almost like salmon. Bull sharks tagged inside the lake have later been caught in the open ocean (and vice versa), with some taking as little as seven to eleven days to complete the journey.
Anatomy and appearance
Bull sharks are large and stout, with females being larger than males. The bull shark can be up to 81 centimetres (2.66 ft) in length at birth and grow up to 3.5 metres (11 ft) and weigh 318 kilograms (700 lb). Bull sharks are wider than other requiem sharks of comparable length, and are grey on top and white below. The second dorsal fin is smaller than the first. Per the Discovery Channel and Animal Planet program Animal Face-Off, bull sharks have a bite force of up to 567 kilograms (1,250 lb).