Observations are one thing, good photography of herringbone seas has turned out to be another.
In nearly every case, the dominant waves stand out better in the photograph than the secondary swell. Although crossing swell, and therefore herringbone seas, occur in nearly every part of the ocean, there is no better place to observe them than in the tropical Pacific Ocean, where sets of swell come from Northern and Southern Hemisphere storms. When the Challenger approached the equator on the first day of November 1985, it was a dominant swell from the northwest and a secondary swell from the southeast that appeared in the sun's reflection. The herringbone sea is seen in the waters to the right of the eddy that was being spun off the Equatorial Current system.