Signs: How to read the sea

We all love looking out to the sea. There is something majestic, calming and hypnotic about the sight of breaking waves and floating ships. The sea holds secrets and if we look closely these secrets are revealed. For a navigator, the sea provides signs that can make a difference between sinking and surviving, between setting adrift and finding land.

Colour of water

Aerial view of Tioman: Notice the different hue signifying the depths and objects underneath

There are four main factors that determine the colour of the seawater we see, mainly what is beneath the water, what is in the water, what is on the water and the effects of light. Since I write this article primarily for looking out signs to help navigation, I will focus on the shade of water for now. Items like salt, mud, salinity, particle and organism content will be discussed in a separate forum.

The colour of the sea holds secrets to what is beneath the water, in the water, on the water and light

Because of the reflection (and refraction) of light on the surface, sea water changes shade with depth. When approaching a land mass from open ocean, you will transition from dark blue to lighter shades of blue to turquoise to green and then white (for sandy bottoms). This knowledge is useful when looking for a place to anchor or while navigating our way out of a bay full of reefs and rocks. Be careful as dark patches in turquoise waters normally mean rocks or corals.

"When approaching a land mass from open ocean, you will transition from dark blue to lighter shades of blue to turquoise to green and then white (for sandy bottoms)"

 The ocean looks blue because red, orange and yellow (long wavelength light) are absorbed more strongly by water than is blue (short wavelength light). So when white light from the sun enters the ocean, it is mostly the blue that gets returned. Same reason the sky is blue.


Tides

"Time and tide will wait for no man"

A good navigator must always know what the tide is doing, coming or going at any time. Tides are caused by the gravitational pull of the moon therefore in an unencumbered space like open oceans, the timing of the tide corresponds to the exact location of the moon in the sky. High tide is when the moon is directly overhead. However closer to shores and in places where movement of sea water is hindered by surface contours, there is a lag i.e time difference between the tides and the moon.


Places like Straits of Melaka until Kuantan have two daily tides (semi-diurnal) while those on northern east coast of the Peninsular and Sabah Sarawak have one daily tide cycle (diurnal).  For places with semi-diurnal tides, the tide will rise for 6 hours to reach high tide and then it will fall for six hours to reach low tide. The cycle continues.

Tide table for Tekek showing times and height of High and Low Water

On a personal note, this information was crucial when I found myself grounded on sandbanks off Beaulieu River or Tulai. Lets say I touched bottom as the tide was leaving three hours before low tide. This means that I will need to wait three hours for the tide to leave until it reaches low tide and then another three hours for it to get back to the level I was stranded at. Then maybe add one or two hours when the boat will release itself from the bottom.

Alright guys, put the kettle on. Time for a cigar! or two.

Note: Tide times shift by an additional 50 minutes a day since they are based on a lunar day, which is 24 hours 50 minutes long.

Spring Tide, otherwise known as air pasang besar happens twice a month.

The difference in height between the sea level at high tides and at low tides is called the tidal range. It can go up to 3.6 meters near Matang, Perak among the highest in the Peninsular.  Twice a month, during a new moon and a full moon, the tidal range is at its maximum for all places. This is when the high tides is its highest and the low tide is its lowest. This is called the spring tide in English, or air pasang besar in Malay. Combined with the monsoon rain, this is normally when flash floods happen in the East Coast.

Waves (Ombak) and Swell (Alun)
It is an easy mistake to say that waves set items adrift at sea. Tides move vertically up and down, while currents move water horizontally left or right. What are waves then? Or for that matter what are swells?

"Angin takde dah, ombak pun kurang tapi alun masih kuat"

A wave is generally caused by wind or earthquakes undersea. It transfers energy across a body of water. Think of it like shaking out a bedsheet. You can see the waves moving through it but the bedsheet remains in our hands.

The difference between a wave and a swell is a matter of magnitude and not so much scientific. A wave can be born and die within three or four hours. A wave might have travelled tens of kilometres. The crest between waves is somewhere less than 10 seconds. A swell can last a week or so and the crest between swells is more than 10 seconds. A swell can travel hundred of kilometres, even outrunning the storm that  gave birth to it. Thus a swell is a good indicator of bad weather to follow.

Crests and Trough on a wave. General rule of thumb is anything beyond 10 seconds between trough should be considered a swell

It is also important to note that a wave that is approaching shallow waters will increase its height. Since it is still carrying the same energy, yet it's wavelength is decreased.

There are places like the Bay of Biscay where seasoned sailors prefer to sail further outside the continental shelf to avoid rough conditions inshore

In 1773 Captain Cook sailed close to the treacherous area in the Pacific Ocean called the Tuamoto Archipelago nicknamed the 'Dangerous Archipelago' as too many ships have smashed into the scattered reefs. Although he could not see them, he 'felt' their presence. He was not psychic. The swell that he was expecting from the south, waves that would have been easily felt was absent. He therefore knew that the archipelago must have been in the south and shielding him from the waters!

The same ripple pattern is true for islands in the oceans. See if you can spot it next time you are out at sea.

Signs: What the night sky tell us

Have you ever had the chance to stare at the night sky in total darkness, when nothing else can be seen?

While it may be the subject of poetry and nice pictures, to a natural navigator it serves as a calendar, a clock, a compass and a map all rolled into one.

Lets start with how we can use the night sky to find direction.

The Moon

You can't really miss the biggest object in the night sky. Every 29 and a half days, the moon goes through its regular cycle.

The different phases of the moon throughout the 29 day cycle

The crescent before the full moon is dark on the left side, while the crescent after the full moon is dark on the right side.

Tip #1 - A line from the horn of a high crescent moon extended to your horizon gives a rough indication of south.

Follow the line from the horn of the crescents down to the horizon and you get the direction of South

A short explaination. From the perspectivce of an observer on the surface of the planet, the sun and the moon travels along the same route on the horizon from east to west.  Imagine a race that starts on the first night of the new moon. Both the sun and the moon starts of at the beginning line on the east horizon at the same time. Since the moon's relative movement is slower than the sun, it lags behind by 12 degrees a day. The bright side of the moon always reflect where the sun is relative to the moon, either on its east or on its west. Hence the line connecting the horn of the crescent with the horizon is always the north-south line.

The Stars and Planets

Tip #2 - Orion sword points south

Stars, planets and constellations come and go from the Malaysian night sky, but Orion remains. Orion is the name of a great hunter in Greek mythology. The constellation (group of stars) look like a hunter holding a club and a shield/bow. Its quite easy to spot. I normally look for a straight row of the three brightest starts closely huddled together. This is called Orion's Belt.

Here's the tip. Extend a line from the tip of Orion's belt all the way to the horizon. Walk towards the point where this line touches the horizon. That will take you south.

Its easiest to spot the three stars in a straight line that make Orion's belt

Tip #3 - Finding Polaris, the North Star

To put it simply, Polaris is uniquely positioned on top of the North Pole. So wherever you are in the world, when you find Polaris the line between Polaris and you points North.  There are a few tricks to find this North Star.

To a natural navigator the night sky serves as a calendar, a clock, a compass and a map all rolled into one

3a. The Big Dipper

For some reason, I find this method the easiest when I was in the UK, but not so in Malaysia. First you need to find something that looks like a dipper (or a senduk in Malay).  Focus on the container and ignore the handle. Identify the two stars that would make liquid spill from the side if you turn the dipper on its handle. In a straight line five portions above will be Polaris. Walk towards the start if you want to go North.

Remember the Dipper, remember North Star

3b. The Cassiopeia

This constellation looks like an asymmetric W.  Imagine across the top of the W. Extend this line two lengths from the star at the middle of the W and you will find the North Star.

Extend a line two lengths of the W from the middle start

Tip #4 - Bintang Timur & Bintang Barat
I sailed overnight once with the son of a fisherman from Kemaman. As we crossed the bit of South China Seas from Sebana Cove to Tioman. He pointed out two the two brightest stars visible in the sky that night, Bintang Timur (East Star) and Bintang Barat (West Star) as the fishermen would call them. As it turns on, these are called Sirius in the east and planet Saturn in the west respectively.

Shipwrecks in Malaysia

In his book Empire of the Winds, Phillip Bowring used the term "Nusantara", a term coined by the Java-based Majapahit kingdom to describe the archipelago that stretches from Papua in the East to Madagascar in the west, Java in the south and Taiwan in the north. He considers this corridor as the worlds "greatest maritime and cultural crossroads, a corridor connecting East Asia, the Arab-Persian world, Europe and the African coast".

The Malay Peninsular was part of the East-West network of ports

Because of its strategic location and the good fortune of being at the meeting point of two monsoons,  for about a thousand years the people of the Nusantara were the middle man for trade between the east and west. Their skills in boatbuilding and navigation enabled them to move cargo like silk and porcelain from China and pepper from this region to places like Gujarat and Musiris on the west coast  of India or Madagascar in Africa where the onward journey would take these goods to Rome or Greece. Goods from the West like glass from Rome and pearls from the middle east also reached China on Nusantaran vessels.

With a thousand year history being at the heart of world maritime trade, it is surprising that more shipwrecks have not been found in the waters surrounding Malaysia.

Location of historical wrecks around the Peninsular

Here are some of the things we know about these historical wrecks (defined as ships that sunk more than 100 years ago).

The Malaysian government has formalized the search and harvesting of these artifacts with Nanhai Marine Archeology Sdn Bhd, a private company specializing in historical wrecks.

Here is a video of one of the dives conducted on the 

Wanli wreck from the company's website.

 

Sukhothai fish and flower plate found on the Nanyang

Sukothai and Satchanalai pottery and cauldrons make up a big chunk of the cargo found

Sukhothai fish and flower plate found on the Nanyang

The wreck at Turiang would have looked like this Chinese Junk

The Royal Nanhai was made of wood native to Southeast Asia combining Chinese and Local shipbuilding technology

Diana was an East India Company tradeship that struck rocks off the coast of Tg Bidara while en route to Madras

The route taken by Diana on that unfortunate night on March 4, 1817

There are still numerous known wrecks that have eluded treasure hunters for decades. For example, in the areas around Cape Ricardo, Port Dickson where a sea battle was fought between the Dutch and Portuguese Armada most of the sunken ships have yet to be be found.

Similarly, in the vicinity of the mouth of Johor River, where Johor Lama once stood there were a lot of sea battles for the control of trade between the French, Dutch, Portuguese and English armada's.

Yet, the biggest catch would be the wreck of Flor De La Mar, the Portuguese Galleon that was used to in the Portuguese conquest of Melaka in 1511. When the city - noted for being one of the richest in the world at that time fell, the booty captured from the fallen kingdom was loaded on to Flor De La Mar to be transported back to Portugal via transit in Goa. According to a contemporary report, it was whilst sailing along the coast of Sumatra that the ship was caught in a storm. An attempt was made to seek refuge on the coast, but the ship was wrecked on a beach. As a result, the ship broke into two, and its back, which was embedded in the sand, demolished by the waves. Along with the ship, the treasure was also lost. 

Flor De La Mar was transporting the war booty taken from Melaka before it sunk in the Straits of Melaka in 1512.

When I sail, I always  wonder what hidden treasures lies beneath the waves.