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Searching the oceans of the most ridiculous largest bony fish.

Photo above: A giant ocean sunfish Mola alexandrini, Nusa Penida.

About Mola

Every year, thousands of divers descend into the waters around the Nusa Islands near Bali, Indonesia in hope to find this gloriously ridiculous fish, the Mola. They do really look like a swimming bin lid combined with spare fish parts. Famous for their comical and weird alien appearance, ocean sunfish are the heaviest boney fish in the sea. Unlike most fish, their skeletons are not made of cartilage, but actual bone, like us. A fully grown Mola can weigh 2,000kg and grow over 3 meters from fin to fin. And it just so happens that the Islands of Nusa Lembongan and Penida are some of the best locations to see them in relatively shallow waters.

They are known by quite a few names, mostly referred to as Mola Mola (the fish so nice they named it twice). Also known as sunfish or moon fish depending on who you ask. There are 6 different species world wide belonging to the Mola genus, but the largest of them found around the Nusa islands is the Giant Ocean Sunfish, Mola alexandrini (not the Mola mola). These animals typically spend much of their life in deeper open ocean, so to see them near the coast is not a common occurrence. Luckily for us divers, they're riddled with annoying parasites from their life in the depths. So these funny looking bin lids then choose to leave the deep waters and approach the reef for a cleaning service. Some tropical reef fish such as long fin banner fish, butterfly fish and even the emperor angelfish have a particular appetite for Mola parasites. Eww gross! Typically this happens during the months of July to October when the cold deep waters rise up to the surface in what is known as an 'upwelling'. During these upwellings in the dry season in Bali the water temps can drop significantly low. The colder the water gets, generally the better chance for finding a Mola. Historically there have been records of temperatures in the peak Mola season dropping as low as 12C. So if you feel the cold be sure to pack a 7mm wetsuit!

When and where to look?

If you dream of diving with a Mola then firstly make sure you're aiming to visit during the months July to October (August/September being the peak). Allow yourself a few days of diving as a minimum to increase your chances. You also want to have an advanced open water certification, if not also your deep diver speciality. That's because typically they are found a depths around 30-40m+. In saying that though I have snorkelled with them before, so you can sometimes get lucky in the shallows too (less likely though). Next you'll need an experienced guide who knows where the frequented areas are and how to find the cleaning stations where the Mola might make an appearance. (see recommendations below for dive operators in Nusa Lembongan). There are many famous dive sites for them such a Crystal Bay, Toyapakeh and Blue Corner to name a few. But to be honest if you want to beat the crowds you can also dive on any of the sites around the islands and have a chance to see them just as often.

The currents

Indonesia is famous for it's strong currents, mostly due to the 'Indonesian through flow'.

This is a current system that connects the Pacific and Indian Oceans. It flows through the Indonesian archipelago's islands, particularly between the islands of Java and Sumatra, and serves as a major pathway for the exchange of waters between these two oceans. This is what contributes to the distribution of nutrient rich waters, species biodiversity and the cold upwellings. But in saying that it can also make diving quite hazardous. So do go with an experienced guide and a dive centre that offers small group (recommendation at bottom of blog).

Photo above: A mola getting cleaned by banner fish, Nusa Penida.

Prepare for the cold

Have you ever experienced a thermocline? This refers to a layer of dense cold water that separates from the warm water at the surface. I mentioned before about the cold upwellings, and trust me it does get proper cold. And it feels especially colder when you start your dive by jumping in to the surface layer where it's 25-28C only to discover that it suddenly drops by more than 10C in mere seconds. It's like getting into an ice bath! You can sometimes even see a shimmering layer where the cold and warm waters meet. This is often when your dive guide will start getting hopeful that there is a Mola riding the upwelling to the reef nearby. There have been records of the water in some areas reaching as low as 12C. This year, in 2023 they recorded 13C and sadly even saw some tropical fish die of shock from the sudden change. But usually its not that extreme in cold months with temps around 17-21C.

How to dive with the Mola

To get most out of your experience with these big fish, here are my tips. You basically want to avoid disturbing them so they don't swim off. Otherwise your encounter will be rather shot. Firstly give them space, they're shy. Secondly, don't chase them or swim at them. Try to be invisible, avoid sudden movements and approach super slowly, giving at least 3m or more space. Avoid flash photography as this often spooks them, their eyes are very sensitive. My top tip is to stay on the reef side of them, close to the corals so they always have an exit should they wish to leave the scene. Really try not to disturb the fish trying to clean them for a longer encounter as well. Be safety conscious, remember if you're seeing a Mola, you're probably quite deep. Therefore keep a close watch on your NDL, depth, air and the conditions. Follow your guide at all times they're there to keep you safe.

Want to name your Mola?

If you do get lucky enough to encounter a Mola on your trip and you got some photos or videos of it. You can contribute to research by submitting the footage and photos to Ocean Sunfish Research. If you happened to see a new one for the database (which is usually the case) you get to name it! How cool is that? Scientists use the spot marking on them like a finger print to track individuals. And since they're still a very mysterious animal, any data you have is incredibly useful. Bonus points if you get shots of each side of the fish! Doesn't need to be professional photos, even GoPro shots are enough.

Recommended Dive Centre for Mola diving:

Siren Diving Lembongan

Nusa Lembongan, Bali, Indonesia.

More Info on diving the Nusa Islands?

If you want some deeper insight into diving around Nusa Lembongan and Penida near Bali, head to my other blog here:

Photo above: Brooke photographing a Mola. Photo by Ollie Clarke

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