On what seemed to be a pleasant morning on the seaside, a group of tourists boating in Pigeon Island National Park in eastern Sri Lanka were in for an unpleasant shock. As they were taking in the rich marine life in the water around them, there was a loud blast close by. They saw that the fish they’d been watching were now either floating dead on the surface or struggling to swim. More dead fish could be seen on the seabed through the clear water.