Best places to scuba dive in September
September is built around the eastern Pacific. Cocos is my first choice for schooling hammerheads and sheer fish biomass. Galápagos has the higher ceiling when cold upwelling is functioning, but recent variability makes it the less automatic booking. Princess Alice Bank is a focused manta trip rather than a substitute for either expedition.
Where should you dive in September?
Cocos Island is the first trip I would book. It ranks #4 overall at 9.5/10, and September sits inside its strict peak window of September — October. Go for hammerhead schools, whale sharks, marble rays.
Read the Cocos Island guide →3 places clear the bar
The order stays tied to the overall ranking. The first card is the answer.
Cocos Island
A long boat ride to a lot of sharks.
You spend roughly a day and a half getting there, and peak season is wet and rough. The trade is hammerheads over cleaning stations, plus whale sharks, marble rays, whitetips and the kind of fish biomass that makes an empty minute unlikely.
- Peak window
- September — October
- Signature
- Hammerhead schools · Whale sharks · Marble rays
Galápagos
Great when the cold water turns up.
In a normal cold-current year, Darwin and Wolf are top-three diving: hammerheads, whale sharks, Galápagos sharks and turtles in the same frame. The warmer water reported in 2026 has made that action less consistent. I would still go, but not without reading logs from the previous few sailings.
- Peak window
- August — October
- Signature
- Hammerheads · Whale sharks · Galápagos sharks
Princess Alice Bank
Mobulas over a seamount in the Atlantic.
Princess Alice is an offshore seamount where Chilean devil rays circle divers in blue water. Tuna and jacks are common enough to matter; blue and mako sharks are bonuses. The boat ride is long and the weather can cancel it, so leave spare days.
- Peak window
- July — September
- Signature
- Mobula aggregations · Tuna · Blue-water seamount