You know how many years people have been serching for Nessie? Since she was first sighted in the year 565. The biggest craze started in 1934, when someone took a picture of Nessie (This was later proven to be a hoax.) Since then, sonar, underwater exploration, and countless other hoaxes have proven Nessie to be an extrememly elusive Cryptid. No one seems able to find her.
Now, about the Bremuda Triangle, methane hydrates from the Continental Shelves (which can stall engines and affects the navigational equipment of planes) or the movement of the North Magnetic Pole (which can mess up compasses) are probably what causes most those occurences. Hurricanes, the Gulf Stream, or even freak waves (This one is the least likely though) can also be culprites.