Wyprawa badawcza Morze Południowe

Deadly currents

If you want to dive or snorkel in or near atolls, you must first learn how the currents work there. Otherwise you are putting your life in absolute danger!

Atolls are basically closed pools on their inside (lagoon). They usually have one or more openings to the ocean, which are called passages. The passages are also the only way for ships to get into the lagoons and therefore often also to the settlements of the inhabitants. There is usually strong surf on the outside of the atolls, which nobody can pass through.

Due to the tides, the water flows into the atolls every 12.5 hours and out again after 12.5 hours. The fewer passages there are, the stronger the current through these bottlenecks. However, the 12.5 hours is only theoretical. Large lagoons fill up more slowly and narrow passages allow the water to flow in more slowly, which shifts the strong current times.

Now you can easily see from the water surface whether and in which direction the water is currently flowing. When the water flows out of the lagoon into the open ocean, waves (called mascarets) form on the OUTSIDE of the passage. If it flows into the lagoon, the mascaret forms on the INSIDE. Diving is only possible when the water is flowing in.

Although the current is as fast as an underground, it flows into the shallow water of the lagoon. As the water flows out, divers may be pulled over a threshold (oceanic step) at the end of the passage into the depths.

But why do you dive into the passages at all?

Because this is where the currents provide the greatest food supply and therefore the most marine life can be found. For experienced divers, it is no problem to drift through the passage with the current and, if necessary, swim into a current shadow behind reef sections to observe fish there.

On the outside at the edge of the passage are the most popular and interesting spots at a depth of 20-40 m to see large sea creatures, including whales. Sharks, eagle rays, tunas, mackerels and barracudas are regular guests.