A slim offshore dolphin that gains spots with age, travelling in large groups in open water.
To about 2.1 m and 114 kg. Slender, with a long narrow beak that has a conspicuous white tip. A dark cape runs from the head to about halfway between the dorsal fin and the tail and is sharply separated from pale grey flanks. The dorsal fin is tall and strongly curved.
The spots are the name and they are acquired. Calves are born plain and become progressively speckled, light on dark and dark on light, until an old animal is nearly covered. Because young animals are unspotted, the reliable marks are the sharp cape edge and the white beak tip. The spinner dolphin, which it often schools with, has three-tone banding and a straighter, more triangular fin.
It occupies the 90 to 300 m layer by day and goes deeper at night to feed on squid and small fish rising from the deep scattering layer. Schools run from several hundred to over a thousand animals and are fast and highly aerial. In the eastern Pacific it is the dolphin that travels above yellowfin tuna, which is why the purse-seine fishery reduced the offshore stock so heavily; that stock has still not recovered, although the species as a whole is not threatened.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.