Where are the fresh water sharks?
By Josh Berman and Randy Wood, Moon handbooks.

How Carcharhinus leucas became the only shark in
the world to be able to pass between saltwater and
fresh water is a facinating story. After thousands of
years of hunting in the brackish outflow of the Rio San
Juan, Nicaragua's freshwater sharks made their way
up the river and formed a healthy population in Lake
Nicaragua. The tale continues with the arrival of humans
and their role as both victims and hunters of Nicaragua's
bull shark. A story recounted well in Edward Marriott's
2001 book, Savage Shore. Indigenous tribes on
Ometepe worshiped the shark, sometimes feeding their
dead to them.

This fear and reverence only faded when the Asian
market for shark fin soup helped to create an industry
around harvesting the famous fish, culminating in the
late 1960s, when Somoza's processing plant in Granada
butchered up to 20,000 sharks a year. Today, the only
fresh water in the world is seldom seen, although it is
still inadvisable to swim in the waters near San Juan del
Norte.