The Earth is large, has the shape of a ball and rotates around its axis. One of the consequences of these well-known facts is the presence of three climatic regions. Polar, where it is always cold, moderate, where it is hot or cold depending on the season, and the tropics, where it is always hot.
The tropical belt is a strip of the globe enclosed between the parallels 23 degrees north and 23 south. Here the sun's rays fall to the ground almost vertically, intensively heating it year-round. There is no cold period, it often rains, the vegetation is rich and lush, plants and fruits grow by themselves, the sea is warm and filled with thousands of different forms of life. This earthly paradise, one of the best regions for those who love the sea and swimming.
And of course, a sailing boat, the best way to enjoy the tropics, like the tropics, is an ideal place for a sailing boat cruise: constant moderate winds, a sea rich in fish, warm water, comfortable temperatures day and night. What more could you want?
However, the situation is not similar to the one to which we are accustomed and it is necessary to study its rhythms and respect the individuality.
Let's start with the islands. Since most of the coral islands are just sandy patches covered with palm trees or bushes, it cannot be expected that they will be visible from afar. Sometimes, with good visibility, the presence of large atolls and lagoons can be seen for a few dozen miles from a greenish reflection in the sky, but you cannot trust this.
The distance of visibility is calculated by the formula
d = 2√h
where d is the distance in miles
h - height of the observed object in meters.
If palm trees (10–20 meters in height) grow on the island, it will not be visible until you reach eight or ten miles, when the crowns of the tallest trees appear over the horizon. When they appear, they represent a strange picture, a stack of vertical sticks, a bit erratic, like the teeth of a broken comb, which grow up and open up on approach.
If palm trees do not grow, and this is just a sandy island, nothing will be visible until the distance of a couple of miles.
Tropical islands are almost always surrounded by coral reefs, which can be adjacent to land (coastal reef) or stretch into the sea for several miles (coral barrier). There are still atolls where there is almost no land. It consists of corals with rare sandy islands.
The coral reefs themselves are very poorly visible, since most of the time they are under water. It is a little easier to notice them when approaching from the windward by crashing waves due to a sharp decrease in depth. A white line of collapsing ridges can be seen at a distance of up to two miles from the coral barrier. On the leeward side, white ridges may or may not be, depending on whether there is a wave. Therefore, you need to approach very carefully, until you notice a change in the color of water closer to the blue, which indicates the outer edge of the coral reef. With good visibility, the color change becomes apparent at a distance of a mile or less.
Coral is a living creature, an agglomerate of billions of microorganisms surrounding themselves with a lime shell and uniting into huge barriers. Growing, they turn into semi-submerged reefs surrounding islands and lands, forming the perimeters of atolls, or just suddenly rise from the bottom, as cathedrals dedicated to Neptune.
Coral reefs, when you look at them underwater, are very beautiful. An endless variety of colors and shapes, underwater grottoes and crevices hidingstanding new surprises. From the point of view of underwater inhabitants, the coral reef is probably an ideal living environment, judging by the incredible diversity of their species, large and small fish, crustaceans, mollusks and many strange and mysterious animals living in close symbiosis with corals. Magical and unique world, the beauty of which is difficult to describe to those who have not seen it.
But from the point of view of the keel of a sailing boat, coral, one of the greatest dangers, is simply rocks, and also sharp. Therefore, the coral reef constantly takes the thoughts of those who have to swim near it. Since it is impossible to avoid reefs, almost all the islands are surrounded by them, it is worth exploring them better.
Today, in many cases, you can rely on large-scale nautical charts that fairly accurately convey the shape and size of coral barriers. Signals such as lighthouses, buoys and landmarks on coral reefs are rarely distributed, and even when they are, they are much less clear and less visible than those to which we are accustomed to swimming in our seas. Sometimes a simple stick stuck in a coral is marked on the maps as an important signal of the navigation situation. You come quietly, in confidence that the barrier is marked, until you approach it very close and then suddenly notice the reef right in front of the boat and a little black curve stick that should be an important signal. And the lighthouses, too, when they are, it is just a fire raised on a simple pedestal no higher than four or five meters.
Thus, regardless of the presence of lighthouses and buoys in reef zones, you can swim only during the day and only in conditions of good visibility, because, after all, only a close look around can ensure the safety of navigation.
How to see a coral reef from a boat? When approaching it, if the sea is calm, brown, yellow or greenish shadows are visible through the transparent thin layer of water. You need to be very careful. The reef often develops vertically, or almost, and then the transition from great depth to the shoals occurs instantly. In order to avoid accidents in such cases, fear helps a lot. This is exactly the case, when coral reefs are near you need to be nervous, concentrated, manic careful, not distracted by anything, often control the map and constantly look around. Take our arrival at Chagos a few years ago.
At thirteen o'clock we go into the strait leading inside the lagoon.
We remove the sails and go under the motor, focusing on the dark color of deep water in the center of the passage. Two minutes of bated breath and convulsive attention, and we are in the inner lagoon.
- What a miracle. - There are no more dangers. There are no more waves and no currents. The water is deep again and we have time to look around and get a better look at the new land we got to.
In fact, there is little land here, but the one that is very picturesque. It appears in the form of an endless chain of beautiful islands, small and low, located around the perimeter of the atoll. And the atoll is so large that the islands have no end in sight.
- It remains only to find where to drop anchor and promise you swimming in the most beautiful place in the world.
- Would rather.
We are heading east to cross the lagoon and stand under the cover of the eastern islands, where in case of strong wind we will be protected by land. It takes half an hour and the islands are approaching. On the inner side of the huge beaches, and then, where the vegetation begins, high thick palm trees. You just need to come up and drop the anchor.
However, two attempts to approach the shore ended in a hasty retreat. Corals rose fromabout the bottom of a vertical wall. On this side of the wall, the depth in the lagoon is more than fifty meters and we cannot anchor. On the other side, the depth is only a few centimeters and one can see how the fish is splashing and jumping in the shallow coral. We make a couple more attempts, then we decide to stop and think. I put the engine in neutral, Lizzy brings the map to the cockpit and we delve into her study, while the boat drifts slowly. We are trying to find a place where the depth decreases more smoothly, but the map is old, the numbers of the depth marks are microscopic and everything seems to confirm that there are no inclines.
- Wait, take the glasses. - says Lizzy and disappears in the cabin. Two seconds pass and I shudder at the piercing sound of the sounder sounder and immediately followed by a terrible blow.
Pale Lizzy appears, I jump to my feet. We look at each other: "Oh my God, we seem to have hit the bottom!"
I run to the helm looking around: the yellow and green shadows of the coral, shining in front and left on the board, confirm that we are going to the reefs. I switch the engine to reverse, give full gas and turn the steering wheel to the right, trying to send the stern to the only zone that I think is free. But in the back of the boat is poorly controlled and does not listen to the helm.
Kiel hits again and my heart trembles with him. Another blow, lighter, finally, the boat is gaining momentum backward and begins to respond little by little to the shifting of the steering wheel. The third blow, I manage to notice how the masts tremble and vibrate along with the guys and shtagami. I'm afraid to even think what will happen if we damage the hull, right here, in the middle of the ocean, where there is no help waiting. A few more seconds and the water suddenly becomes deep again, the echo sounder is silent and shows twenty-five meters. We are scared and disoriented.
- How could this happen?
- I have not seen anything.
- What a frivolity!
Fatigue after the transition, the lagoon with its pastel colors, calm water after so many days at sea relaxed us to such an extent that we forgot the most basic precautions. Instead of one to stand on the steering wheel and the other to look from the mast, out of inexplicable folly we both sat in the cockpit, studying the map, while the boat drifted to a separate reef.
So, never get distracted!
In terms of visibility, optimal conditions for swimming between reefs when the sun is high and better from the back, and the surface of the water is a little ruffled. In such conditions, if the water is clear, and it is almost always transparent, you can safely go forward, even if you have to twist the slalom between the corals. It is much worse if the sun is covered with clouds, and especially if the surface of the water is smooth, because smooth water reflects the gray color of the sky and is completely invisible what is under it. Even worse, when the sun is low and is right on the course. In this case, the reefs become completely invisible and swim between them in such conditions should be avoided. Therefore, when planning to approach the islands after the transition, or just moving from one island to another or from one anchorage to another, you need to count so as to arrive around noon when the sun is still high and you can go in all directions. If the direction of entry into the lagoon coincides with the east, you can arrive in the afternoon, as the sun in the west will not interfere, if you do not risk to enter the west, you need to have time before 15.00.
Visibility of the bottom is improved if you use sunglasses with polarized glasses (Polaroid), which eliminate part of the glare on the surface of the water, and is improved even more by lowering the observation point. WITHnasal flap can be seen better than from the deck, with splinters can be seen better than from the railing.
The higher you climb, the better you can see the bottom and its relief. On the other hand, when the water is clear, the higher you are, the more difficult it is to estimate the depth. A good compromise, a comfortable position sitting on Kraspitsah. With time and experience, one glance is enough to choose the best passage.
When swimming close to reefs, one often has to deal with currents, ebbs and flows, which sometimes make swimming very difficult, especially when one has to overcome channels called passé, which lead to the inside of the atoll lagoon. The problem is that all the water that must enter or exit the lagoon at high tide or low tide rushes into this narrow channel, and the flow into the passe can be very strong. The flow depends on the tide phase, it disappears when it is high and when water is low, it flows inwards when the water comes in and out when it decreases. Between the tidal phases there is a moment when the flow for some time stops altogether, in order to change to the opposite in a few minutes.
Naturally, these moments are optimal for the passage of the channel. If the channel is sufficiently deep for passage into low water, the optimal moment, a little before the end of the ebb tide, a low-flow current makes it possible to maneuver better even at low speed relative to the bottom, and it is easier to stop in case of unforeseen obstacles. If the depth is not sufficient, then it is necessary to go into high water or at the very beginning of a low tide.
It must also be remembered that the drop in sea level at high tides increases into syzygy, that is, with a full or new moon, and then stronger currents must be expected in the channels.
When an atoll has several channels, it is better to choose one that is upwind from the lee side, more protected from the ocean wave. Inside the lagoon, there is usually a sandy bottom alternated with intermittent corals of various sizes. The depth inside the atoll can vary greatly, from a few dozen centimeters in the Aldabra atoll in the Seychelles, very beautiful, but inaccessible to the yacht, to more than forty meters, as in the Maldives, also beautiful and almost also inaccessible, though for opposite reasons. If a leeward canal is chosen to enter the lagoon, then for parking it usually goes to its windward part, under the shelter of the coral barrier, where protection from the prevailing winds is better.