Figure 1. Rolled swimming in great hammerhead sharks Sphyrna mokarran.

For a to d, roll and pitch angles were measured by an electronic tag attached to a 295 cm shark's dorsal fin, and monitored as it swam freely at the Great Barrier Reef, northern Australia. (a,c) A typical hour-long time series for that animal. (b,d) Probability distributions of roll and pitch angles based on the last 15 h of the monitoring period for the Great Barrier Reef shark. Images in e,f were taken with a fin-mounted video camera attached to another wild S. mokarran (∼350 cm) as it swam rolled to the left and right (respectively) at South Bimini Island, the Bahamas, at absolute roll angles of ∼60° (see Supplementary Movie 2 for examples of this and other wild S. mokarran swimming rolled).