Sonars, archives and other toys

It’s a known fact that the bigger the boys, the bigger the toys (not to mention the egos! ) Our team is made up of boys who are now quite grown up, so we have plenty of toys! Bringing those 12 full bags to Sierra Leone is finally starting to yield some interesting results.

-- Advertisement --

For the past few days we have been cruising around the island with sonar. For wreck divers it is a device known as a brush to a painter. For those who are not familiar with it, a word of explanation: the water is not very clear for light – you can usually see a few dozen metres under water. However, it is extremely hospitable for acoustic waves, which it conducts a thousand times better than air.

Scientists invented many years ago that it is possible to send out pulses of these waves and to listen for the echo that comes back – just like a bat searching for an insect, but underwater. And in this way you can locate various objects on the bottom.

None of this type of equipment – of course – can be obtained in Sierra Leone. So we brought both the fishfinder (which “sees” what is going on directly under the boat), and the side scan sonar towed behind the boat – which is blind to what is directly below us, but can see 100 metres to the sides.

So we swim with the sonar and stare at the laptop screen to spot something unusual on this sandy and rocky bottom. We have already pinpointed a few interesting locations (one of them in the picture – bottom left corner), which we are gradually checking. Sometimes they are only rocks, sometimes remains of wrecks, sometimes it happens that the current under the water is so strong that it is impossible to check the place. Then we come at a different time, when there is a minimum or maximum tide and the water movements are the weakest. Looks like something interesting will come out of it!

Even more interesting is the study of this wreck with 20 cannons, which we have been exploring for several days, and which no one has yet examined since the day of its discovery. We are mapping it, drawing the cannons and anchors, searching the nearby stones.

We have heard back from Mr Rafał Reichert, a Polish underwater archaeologist working in the Caribbean, who has looked at photos of our anchors and claims that this is a type characteristic of ships that sailed the oceans from the 17th to the mid-18th century. The latter agrees pretty well with the date on the gun – 1762 is just over the middle of the 18th century.

Yesterday we also ventured a little below the wreck to the sandbanks, where we found several broken fragments of beautiful (Chinese?) porcelain. Today we will try to work with the ejector in this area, maybe we will be able to uncover more monuments!

Source: Organiser