Experience Blackwater diving in Rarotonga

Blackwater diving in Rarotonga

Scuba dive Rarotonga at night in the deep, open ocean. Witness the largest migration of biomass on our planet with Adventure Cook Islands blackwater diving trips in Rarotonga.

Imagine you are in the middle of the ocean, with 1000 to 2000 metres of water below you. It is a pitch black night, there is no moon, no wind and the the ocean surface is flat. Only a weighted line with attached lights illuminates the water. As you dive down, you see that you are surrounded by countless of tiny critters. You are observing the largest migration of biomass in the world: the diel vertical migration. This is blackwater diving. Nowhere else in the world will you feel as close to being in outer space.

The diel vertical migration

Juvenile boxfish on blackwater dive

During the diel (or diurnal) vertical migration, millions of tiny creatures called zooplankton migrate every night in the cover of darkness from the deep oceans up towards the surface. At the surface, these miniature crustaceans and jellyfish feed on the phytoplankton, which are microscopic size plants. At the end of the night, the zooplankton must make their way back to the safety of the dark, deep ocean to avoid being eaten. During this ever repeating synchronized movement through the water column, the zooplankton is followed by a large number of predators that feed on this seemingly endless food source.

How is the dive conducted?

Juvenile flounder on blackwater dive in Rarotonga

We only have to drive one to two miles away from the reef as the ocean gets deep very quickly. Once we are in deep water, we stop the engine and let the boat drift. We then lower an illuminated line to about 20 metres. Even though the water is very deep, blackwater dives are shallow dives, usually between 5 and 20 metres. During the dive you will drift alongside the boat with it’s submerged, brightly illuminated line that serves as reference as well as to attract critters.

Sightings on a blackwater dive in Rarotonga

Flyingfish on blackwater dive in Rarotonga

During a typical blackwater dive in Rarotonga, you will see countless of tiny crustaceans, jellyfish, fish larvae and juvenile fish. You will also often see hunting squid as well as flying fish hanging out close to the surface. These are not dives to observe big marine life. In fact, the majority of the most amazing critters are only a few millimetres in size.

Who is blackwater diving for?

Our blackwater dives in Rarotonga have been designed with the experienced underwater photographer in mind. However, all experienced divers are welcome on our blackwater dives, as long as they have a minimum of 50 logged dives and have recently dived with us.

When we dive

For everyones safety and enjoyment, we only conduct blackwater dives in Rarotonga when sea conditions are extremely calm and when there is hardly any wind. Rarotonga is a small island in the middle of the massive South Pacific Ocean. The small island offers no protection from the wind when you move away from the reef. Conditions are often not calm enough to conduct blackwater dives. Therefore, we do not take blackwater diving bookings in advance and all blackwater diving enquiries have to be done at our shop when on the island.

Blackwater diving is usually best around new moon. Nonetheless, when sea conditions are calm, we also conduct blackwater dives during other moon phases.

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