When It Rains, It Bites

Heavy rainfall is getting more intense as the climate warms. Sharks are noticing. Researchers are now drawing a direct line between extreme weather runoff and rising human-shark encounters near shore, and the mechanism is more layered than you'd expect.

The story starts on land. When intense rain hits a coastline, it doesn't just drain into the sea and disappear. It changes the water itself, shifting salinity, dropping visibility and altering oxygen levels. That cascade reorganizes who's near the beach and why.

Heavy rainfall flushes more nutrients out to sea, drawing higher fish populations toward shore. Baitfish move inshore. Sharks follow baitfish. It's not complicated, except it is: while the influx of fresh water may help attract baitfish closer to shore, lowered salinity also drives some shark species away. The picture isn't simply "more rain, more sharks everywhere." It's more rain reorganizing the whole system.

Increased sediment following intense rain raises its own risk by reducing visibility, making it harder for sharks to see and avoid people. That last part tends to get left out of the headline version: visibility cuts both ways.

Four recent shark incidents in New South Wales followed an intense rainstorm that flushed runoff into coastal waters. A 2019 study found tiger and white sharks are more likely to bite after heavy rainfall. Bull sharks, believed to be behind some of the recent incidents, are more common in local waters during warmer months, which is also when more people are in the water.

Extreme rainfall is expected to increase as the atmosphere warms and holds more water. This is less a freak coincidence and more a preview.

The ocean hasn't changed its rules. The rain is just delivering more people and more sharks to the same address on the same days.

Read the full story at Scientific American, July 8, 2026

Hot Take: The part nobody wants to sit with is that the sharks aren't doing anything wrong. The runoff reshuffles the deck and suddenly there's a predator in murky water it can't see through, near prey it can't clearly identify. That's not aggression. That's a Wednesday for an animal that evolved 450 million years before we started paving coastlines.