Usually from November until May. During this time the sea is at its calmest. Great monthly overview with a wildlife calendar: http://www.divereport.com/locati...
Mid January to end of March you may have the chance to snorkel or even dive with humpback whales.
Stunning ocean wildlife: Giant mantas, whale sharks, bottlenose dolphins, humpback whales!
Socorro is popular for the friendly giant mantas which come very close to divers, often it's less than 1 meter. The average size of these mantas is impressively 5--6 meters. Also the bottlenose dolphins are accustomed to divers and may come very close. Have in mind water temperature at the humpback season is less than 25 degress.
Socorro Island is one of four vulcanic islands in the pacific ocean which are called Revillagigedo Islands, or "little" Galapagos.