Present at the archipelago from about January to April, when the song is often audible underwater long before anything is seen.
To about 16 m. The Revillagigedo Islands are a breeding and calving ground for the North Pacific population and the animals are present from about January to April, with the peak in February and March. Song carries a long way underwater and on most dives in season it is audible for the whole dive without anything being seen; a diver hearing it for the first time usually mistakes it for a boat or for equipment noise.
What a diver actually gets is unpredictable. Encounters happen in open water between the islands and off the rock rather than on any particular site, and they are a matter of the animal choosing to come, not of being found. Approach is regulated inside the national park and the operators run it to those rules: no pursuit, no diving on a mother and calf, engines out of gear. A whale that approaches a stationary group of divers has made its own decision, and the correct response is to stay still and let it.
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.