The waters around Príncipe lie in a stretch of the Gulf of Guinea that supports year-round cetacean populations. Humpback whales pass through between July and October, when they gather in the warm Gulf of Guinea waters. Spinner dolphins and bottlenose dolphins are present throughout the year and are often encountered on boat trips between the island's beaches.
Boat excursions from Santo António harbour can be arranged through local operators and guesthouses. The usual format is a half-day trip that combines dolphin spotting with snorkelling at one of the offshore islets. Humpback sightings are not guaranteed but are reasonably common in the peak months of August and September when the whales congregate to feed.