Some dynamite and a plastic bottle. That’s all it takes for a fisherman to kill hundreds of fish and transform thriving coral reefs into rubble in a matter of seconds.

Around the world, fishermen are using explosives, often with dynamite, to maximize their catch. Called blast fishing or dynamite fishing, the practice goes on in nations from Lebanon and Malaysia to the Philippines, while some countries—Kenya and Mozambique, for instance—have managed to stamp it out.

In Africa, Tanzania is the only country where blast fishing still occurs on a large scale—and it’s happening at unprecedented rates. “I would say probably for the last five years it’s at least as bad or worse than it’s ever been,” said Jason Rubens, a marine conservationist