Bali: Awash in World’s Best Dive Sites

By Sophia Read
For The Bali Times

SEMINYAK ~ Indonesia is a divers’ Mecca for one main reason – the marine life here is amongst the most diverse in the world. The Caribbean has only a quarter the genera of coral (approximately 20, compared to Indonesia’s 80), and less than one third the number of species of fish (approximately 800, compared to more than 2,500 species found in Indonesian waters).

Indonesia has 14 percent of the reefs of the entire globe, and, despite the lack of proper studies, they probably harbor the richest marine ecosystems on Earth. There is one main contributor to this – the Arus Lintas Indonesia, or the Indonesian Throughflow.

There is a 30-centimeter difference between the level of the ocean to the north of Indonesia and that to the south. And, as we all know, water flows inexorably downhill, creating this Indonesian Throughflow. In the north the Trade Winds trap the water of the Pacific, raising sea level to 15 centimeters above normal. The Indian Ocean to the south of the country is 15 centimeters below average sea level.

Look at a map of Indonesia – look at the horizontal stretch of the country from west to east, bordering the vast expanse of the Pacific Ocean. Imagine all that water, forced by gravity, into the Indian Ocean to the south. Normal measurements simply did not suffice (or rather the magnitude of the numbers involved proved unwieldy) to express the sheer volume involved – scientists had to invent a whole new scale of measurement: the “Sverdrup”.

The concept of a Sverdrup is best captured in the diver’s bible, Diving Bali by David Pickell and Wally Siagian.

“Think of a river 100 meters wide, 10 meters deep and flowing at 4 knots – then imagine five hundred of these rivers. That’s one Sverdrup of flow. The Indonesian Throughflow, scientists estimate, represents 20–22 Sverdrup, or 10,000 of these rivers.”

Take another look at that map of Indonesia. It is an archipelago of well over 17,500 islands, forming a rather effective dam. Water (as anyone who has ever suffered a flood in their house knows) will find a way. The reefs of Indonesia act as effective filters, offering a new home to all the marine life washed through from the Pacific.

Bali is in an enviable position in Indonesia, as not only does the massive flow of water from the Pacific bring an incredible variety and amount of plankton to the reefs, but the water from the Indian Ocean, with its own load of different species, also reaches Bali seasonally every year. That the best sites in Bali are in the north and northeast is no coincidence, as the Lombok Strait is one of the few channels through which the water from the Pacific can reach its destination, and the reefs are ideally placed to catch the remarkable array of plankton, juvenile fish and coral swept along by the force of the flow.

The force of the flow through the Lombok Strait brings the richer waters from the deep up to the surface, which carry an astounding variety of marine life, constantly rejuvenating and reinvigorating Bali’s reefs. This contributes to the incredible recoveries from devastation that we have seen in recent years, after the plague of Crown of Thorns Starfish and an El Nino event in the late 1990s nearly wiped out the shallow reefs at Bali’s oldest dive site, Menjangen Island.

It also, however, explains why, when talking about currents around Nusa Penida, divers’ eyes go wide – imagine diving with Sverdrups!

The writer is sales director of AquaMarine Diving – Bali

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