Large predators expend large amounts of energy foraging for prey based on expected high return. Documenting how they manage costs and benefits of feeding is difficult, particularly for marine predators. Here we combined animal-borne video, accelerometry, depth sensors, and biomechanical principles to examine behaviour and estimate energetic cost, during white shark (Carcharodon carcharias) breaching – a behaviour where sharks launch from the water while attacking Cape fur seals (Arctocephalus pusillus pusillus). We show that breaching begins at depths up to 20 m, is characterised by a brief (~ 7-16 s) ascent to the surface during which pitch angle increases by ~30 °, and tail-beat frequency increases by a maximum of 6.5-fold (0.39 to 2.50 Hz). This increase in tail-beat frequency equates to an estimated 7-fold increase in energetic costs during a breach. Sharks also demonstrated the ability to rapidly adjust their approach to the seal during ascent. Tail-beat frequency during breaching was ~2-4 times higher (0.83-1.67 Hz) than during non-predatory ascents (0.4 Hz). Biomechanical considerations suggest that breaching attacks require 1.8-3.3 times more energy than non-predatory ascents. This highly energetic tactic leads to high rates of predation success, exemplifying the high cost/high return foraging strategy of top predators.