Quick answer: Take a morning boat trip from Jungutbatu: Mangrove Point on Lembongan, then Crystal Bay and the manta cleaning stations off Nusa Penida, where reef mantas are seen all year. Always go with a licensed boat, as currents are strong.
Lembongan, Ceningan and Penida sit in the Badung Strait, where deep ocean water moves between the Indian Ocean and the seas to the north. That flow brings nutrients, cool water and big animals, and it also means currents can be strong and change quickly with the tide.
Snorkelling spots
Mangrove Point
At the northeast tip of Lembongan, near the mangrove forest. A gentle drift over shallow reef when conditions are right, and a common first stop for snorkel trips.
Crystal Bay
On the west coast of Nusa Penida, a short boat ride away. A sandy bay with a reef drop-off, popular with snorkellers and divers.
Gamat Bay and Toyapakeh
On Penida's north coast, facing Lembongan. Coral slopes and lots of fish, usually visited as part of a boat trip.
Manta rays
Reef manta rays gather at cleaning stations off the southwest coast of Nusa Penida, at Manta Point and Manta Bay, where small fish pick them clean. Studies have recorded them there all year round. Trips leave from Lembongan in the morning; the open-water crossing to the manta sites can be rough, so it isn't for people who are nervous in swell.
Keep a few metres away, don't touch them, and don't swim down on top of them. Let them come to you.
Mola mola, the oceanic sunfish
The sunfish lives deep and comes up to the reefs around Penida to be cleaned, mostly in the cooler months, roughly July to October. It is mainly a diving encounter, at depth, and never guaranteed. More on the seasons.
Learning to dive
Lembongan has several dive schools that run beginner courses on the calm reefs before taking you to the bigger sites. Ask about the instructor's experience with local currents, the group size, and what happens if conditions are bad on the day.
Questions
Can you snorkel with manta rays from Nusa Lembongan?
Yes. Boat trips leave Lembongan in the morning for the manta cleaning stations off Nusa Penida's south coast, where reef mantas are seen most of the year.
Where is the best snorkelling on Nusa Lembongan?
Mangrove Point at the northeast tip is the classic first stop. Crystal Bay and the north coast of Nusa Penida are a short boat ride away.
Is it safe to snorkel on Nusa Lembongan?
Yes with a licensed boat and a guide. Currents in the strait can be strong and change with the tide, so don't snorkel far from shore on your own.
Is the water cold around Nusa Penida?
It can be. Cold upwellings can drop the temperature suddenly, especially July to October. A thin wetsuit helps.
Beaches for swimming
Yellow Bridge and Ceningan
Blue Lagoon and cliff jumping