September is prime mola mola season around Nusa Lembongan and Nusa Penida – and nowhere is that more true than at Crystal Bay, the world-famous cleaning station where these giants come within reach of recreational divers.
The cooler waters of the Indonesian dry season draw one of the ocean’s strangest animals up from the depths.
Mola – better known to most divers as mola mola or ocean sunfish – spend much of their lives away from the reefs, but at this time of year, diving with Emperor Divers Nusa Lembongan gives you one of the best chances anywhere to meet one.
It’s one of the reasons divers travel from around the world to this corner of Indonesia. But what exactly is a mola, and what do we know about the extraordinary life it leads when we’re not lucky enough to see one?
First, is it actually a mola mola?
Here’s an interesting place to start.
Divers around Nusa Lembongan and Nusa Penida have traditionally called these enormous fish “mola mola”. However, research has established that the species regularly encountered around Nusa Penida is Mola alexandrini, the giant or bumphead sunfish, rather than Mola mola, the ocean sunfish.
The familiar name has stuck – and you’re still likely to hear everyone talking about “mola mola season” – but scientists now have a much better understanding of the different species within the sunfish family.
Mola alexandrini is a true giant. The largest confirmed specimen weighed nearly 2,750kg, making it the heaviest bony fish ever recorded.
Why do they look like that?
There’s no mistaking a mola.
Its enormous, flattened body appears to end abruptly, almost as though someone forgot to finish drawing the fish. Instead of a conventional tail, it has a rounded structure known as a clavus, while its large dorsal and anal fins provide the power for swimming.
The name makes perfect sense too. Mola is Latin for “millstone”, a reference to its huge, rounded shape.
That strange design once contributed to a misconception that sunfish were rather passive animals drifting wherever the ocean took them. Research has instead shown them to be active swimmers capable of travelling considerable distances and making repeated dives into deep water.
What does a mola do all day?
A lot more than you might imagine.
Sunfish move up and down through the water column, with studies recording them hundreds of metres below the surface. Feeding is one reason for these journeys, with gelatinous animals such as jellyfish and salps forming part of a diet that also includes other marine creatures.
Those deep dives expose them to considerably colder water.
This may help explain another famous piece of sunfish behaviour: apparently basking at the surface. Scientists believe returning to warmer surface waters can help sunfish raise their body temperature after time spent feeding at depth.
So that mola lying on its side at the surface isn’t necessarily being lazy. It may simply be warming up.
Why do they visit the reefs?
This is where Nusa Lembongan and Nusa Penida become particularly important.
Sunfish can carry numerous parasites, and visiting a cleaning station allows much smaller reef fish to remove them from their skin, mouths and gills.
For the mola, it’s effectively a trip to the spa.
For divers, it’s an extraordinary opportunity.
Instead of an open-ocean animal simply passing in the blue, a mola may remain around a cleaning station while bannerfish and other reef fish get to work. Watching an enormous sunfish hovering almost motionless as comparatively tiny fish fuss around it is one of diving’s great wildlife encounters.
Why is September such a good time to see mola?
Mola can be encountered at other times, but the main season around Nusa Lembongan and Nusa Penida generally runs from July to October, with August and September among the key months.
Seasonal upwellings bring colder, nutrient-rich water towards the reefs, creating the conditions associated with mola moving into shallower water and visiting cleaning stations.
Crystal Bay is the most famous site for encounters, although mola are seen at a number of dive sites around the islands.
And that’s why this is such an exciting time to be diving from Emperor Divers Nusa Lembongan. Being based locally gives our team access to the surrounding dive sites and the opportunity to plan dives around the conditions.
Of course, these are wild animals. There are no guarantees – and that’s part of what makes an encounter so special.
How should you behave if you see one?
The temptation when a mola appears is obvious: swim towards it. Doing the opposite can produce a much better encounter.
Stay calm, maintain good buoyancy and give the animal space. Don’t chase or touch it, and avoid getting between the mola and the cleaning station or its escape route into deeper water.
Allowing the fish to determine the encounter is better for the animal and may give you considerably longer to enjoy the experience.
Where else can you find sunfish?
Sunfish aren’t exclusive to Indonesia. Members of the family occur widely through tropical and temperate oceans, and Mola alexandrini has a broad distribution across the world’s major oceans.
Within Indonesia, mola encounters are also possible beyond the Nusa Islands, including areas explored by liveaboards, but they are far less predictable. For anyone specifically hoping to see one while diving, Nusa Lembongan and Nusa Penida remain among the world’s standout destinations.
Emperor’s wider Indonesia liveaboard itineraries offer a different reason to explore these waters, taking divers into destinations including Komodo and Raja Ampat for coral reefs, manta rays, sharks, macro life and the remarkable diversity for which Indonesian diving is famous.
A giant we’re still getting to know
Perhaps one of the most appealing things about the mola is that, despite its enormous size, there is still plenty we don’t know about its life.
Modern tagging and research have transformed the old image of a sluggish fish drifting around the ocean. We now know sunfish travel through huge areas of open water, dive deep in search of food and make sophisticated use of different water temperatures.
And for a few months each year around Nusa Lembongan and Nusa Penida, these normally elusive ocean travellers come within reach of divers.
They may look like one of evolution’s strangest experiments.
But the more we learn about the mola, the more remarkable they become.
If you would like to find out more about diving with Mola mola (or Mola alexandrini…) contact our excellent team on [email protected] and they will do all they can to help.
