Pacu

Staci-Lee Sherwood, Sea Turtle Oversight Protection

South Florida is at the height of sea turtle nesting season, the time of year when thousands of turtle hatchlings burst out of their nests and instinctively use moonlight to guide them out to the ocean.

Although conservationists have made progress in dimming the lights along the beach, they're still running up against a form of light pollution that's hard to control.

The appearance of a Brazilian fish has sent a chill through summertime swimmers in Sweden and Denmark. The alarming fish isn't the much-feared piranha but its cousin, the pacu, which has large teeth and a reputation for attacking men's testicles.