This aim of this study was to establish safe thresholds for farmed salmonid fish from underwater detonations. The navy detonate charges either within naval training ranges or during dumped munition clearance operations. In Norwegian water, both activities typically happen near fish farms. Experiments with five detonations of 2 kg TNT with 1 h interval 3.5 km from a fish farm in Korsfjorden, Norway, were conducted. The fish farm contained five pens with rainbow trout between 200 and 700 g. Underwater cameras were used to monitor the behavior of the fish. Food consumption and mortality were recorded daily from 1 week before to 1 week after the detonations. In addition, fish were sampled daily from the closest pen, before and after the detonations, for pathological examinations focused on barotrauma. Behavioral stress reaction was not observed in any of the fish pens during exposure to the impulse sounds from the detonations. No significant change in food consumption nor mortality was found, and there was no pathological findings in the exposed groups nor the control groups. Based on these results, and another similar study conducted earlier, the authors consider 170 dB zero-to-peak pressure (re1μPa) in the hearing band of the fish (20–500 Hz band), and 180 dB broadband zero-to-peak pressure (re1μPa), safe thresholds which would not lead to direct or indirect impact on farmed salmonid fish.