The Galápagos Islands don't have a single dive season so much as two distinct ones, shaped by which ocean current is dominant at a given time of year.
The cool season runs roughly from June through November, peaking between June and October, when colder water moving through the archipelago brings a surge of marine life. This is when divers see larger schools of hammerhead sharks, adult whale sharks, giant manta rays, and a broader range of visiting species drawn in by the nutrient-rich conditions. The warm season, running roughly from December or January through April or May, brings calmer, clearer, warmer water, but a narrower range of marine life — sea lions and turtles remain present nearly year-round, while the big schooling pelagics become less reliable.
Water temperature also varies significantly by region within the islands, not just by season. Near Wolf and Darwin, the northern sites most associated with hammerheads and whale sharks, water hovers around 24°C (75°F) during warmer stretches. Farther west and south, around sites near Isabela Island, upwelling from a different current can drop temperatures to around 17°C (63°F) even when it's warm elsewhere in the archipelago. That gap matters for exposure protection and for understanding why dive briefings often describe conditions site by site rather than as a single archipelago-wide number.
Because of these current-driven conditions — cooler water, occasional strong surge, and depths where hammerheads are commonly encountered around 20 meters (65 feet) — most Galápagos liveaboard operators set a higher certification bar than many other destinations. An Advanced Open Water certification is typically the minimum required, along with a minimum number of logged dives, commonly cited at around 50, before a diver is accepted for the northern sites.
For anyone weighing when to go, the honest answer depends on the goal. Divers chasing the largest schools of hammerheads and a shot at whale sharks should aim for the cool season despite the colder water. Divers prioritizing comfort, visibility, and a more relaxed experience — while still expecting reliable sea lion and turtle encounters — may prefer the warm season instead.