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The aim of this study was to examine how the activities and energetics of bottlenose dolphins off Choros Island, Chile, are affected by boats. Swimming speeds and movements of dolphins were recorded via theodolite tracking (n=21.3 observation hours). The results show that close boats (<100 m) affect the behaviour of bottlenose dolphins more strongly than boats further away (>100 m). The activity budget of dolphins did not change significantly with distant boats compared to controls. Close boats, however, induced a decrease of feeding (from 6% to 0%), resting (15% to 5%) and social behaviour (15% to 5%). The proportions of high-speed swimming (5% to 11%) and slow swimming (20% to 38%) increased. In the presence of close boats, dolphins were observed 6 times more frequently to leap and 3.6 times more frequently to tail-slap than under control conditions – an indication of disturbance. Dolphins responded to close boats with evasive manoeuvres similar to predator avoidance. With more than two close boats, animals swam approx. 37% faster than without close boats – a horizontal avoidance strategy. Diving as a vertical avoidance strategy constituted 16% of dolphin reactions towards close boats. In 14% of the cases, there was a simultaneous occurrence of horizontal and vertical avoidance behaviour. That was mostly the case, when several boats stayed a long time in the proximity of the dolphins. An energy consumption of 2.93 W kg-1 was calculated. This corresponds to a daily energy demand of 50.6 MJ per dolphin assuming 200 kg body mass. With boats at close range, the mean power requirement of dolphins was around 15.4% higher than during controls. With close boats, dolphins used a third of their energy budget to avoid boats by swimming at high speed. In the light of these findings, recommendations for dolphin-watching guidelines are given