SHARKS GET EVEN SCARIER

Florida Atlantic University researchers anchored a boat off Palm Beach County, deployed an underwater speaker that drifted up to 62 feet away, and parked a drone 130 to 165 feet overhead to film what wild blacktip sharks would do about it. The sounds were played loud enough to startle the sharks rather than lure them, so this was a jump-scare study. It worked. The sharks picked up the noise from 74 meters out, about 243 feet, and cut hard in the opposite direction. The team ran three low-frequency bands, 100 to 200 hertz, 200 to 400, and 400 to 800, plus a 10 kilohertz control tone that sits outside known shark hearing. The sharks responded to all three real ones and ignored the control completely, which is the closest a fish gets to leaving you on read. More than 70 percent of the reactions happened in the acoustic far field, and lower frequencies got noticed from farther away. How they do it is still open. Sharks have no swim bladder, the gas-filled organ many bony fish use to sense sound pressure, so suspicion falls on the inner ear and a structure called the macula neglecta reading particle motion. Lead author Caroline Sullivan said testing this in a tank is "like being in a house of mirrors," with sound bouncing off every wall, which is why they went out and did it on real sharks in real ocean.

Why you should give a shit: Every blacktip within 80 yards hears you belly-flop off the boat, and the study's actual finding is that a loud noise sends them away rather than toward you.