It is 5.00 am in the morning (20 October, 2021) and Captain Mike and I are wide awake trying to figure out wtf happened last night on Knowind.
We left our ancorage at 2.45 pm yesterday afternoon armed with our new permit and very proud that we could legally anchor in Kraalbaai, a premier anchorage in South Africa.
Situated in the Posberg nature reserve, we knew we would be safe from the oncoming cold front. Captain commented at the time that it was better to leave 2 hours after high tide so that if we got stuck it wouldn’t be forever as the following tide would give us enough depth to get off wherever we might be stuck again. Full moon and spring tide with a 1.7 metre tidal range. Although we were only moving 2 miles away, the channel is incredibly narrow and tricky. 50 metres off course port side and there is suddenly a pole and NO water!
We use the Navionics app on our smart phones on deck but also have a Garmin chart plotter inside with purchased charts for this area. We edged cautiously into the bay, watching our depth sonar at all times. Navionics showed a depth contour exceeding 2 metres which represents the lowest depth on the biggest spring tide.
Captain Mike, with over 20 years sailing and anchorage experience, dropped the anchor with all systems telling us we have 2 metres under the keel. Lit the braai fire, perfect still evening, 4 houseboats all occupied around us. This is heaven.
Around 7.30 pm Captain went downstairs for a nap and I was still on deck enjoying the sunset and peacefulness. Suddenly I felt the deck moving under my feet and I am starting to slide off my seat! First thought was “how pissed am I?” Second (stupid) thought was “there’s a whale under us. ” Dashed to hatch and shouted to captain below who woke up immediately but couldn’t get off his couch as by now the boat had tilted by about 30 degrees. The port side railing of the boat was under water within minutes.
Absolute chaos inside, 2 dive bottles became aqualung projectiles, tools were lying around as we had not stowed away anything on our short 2 mile passage, you name it, it flew across the cabin! I, unfortunately, had an extreme phsycotic reaction as it was exactly the same fear and circumstances (shit flying about) when we lost the mast in the Atlantic ocean. Read about it here if you have not already done so. Captain didn’t help much when he told me ” it’s going to get worse as we will drop another 20 cm” and the water was already lapping on the rail outside! I envisioned the boat lying on her side in the sand and me in a watery grave. I really did. After much a’weepin and a’wailin he sent me to bed with a stiff whisky! Woke up at 4 am and we were upright, yay! Yanked up the anchor and moved about 200 metres away. Where it shows a depth of 2.8 metres on the the Garmin and Navionics.
So, what happened?
We got here an hour after high tide.
Dropped anchor where Navionics showed a 2 metre depth contour. That means that the depth will never be less than 2 metres below us even at low tide.
On a boat your sonar shows the depth of the water below your keel. Our keel is 1.8 metres. Our sonar showed 2 metres depth which means we had 2 metres below the keel at that moment which was high tide. Even if the boat “dropped” 1.7 metres which was the tide difference yesterday, we should have still been perfectly safe and clear.
So, why did we land on the ground and tip over? The only logical explanation seems to be the following:
The sonar, from which we get our depth reading, is placed pretty far forward on the boat so was inaccurate in relation to the keel.
Navionics has clearly not given an accurate depth as their app shows a depth of 2 metres.
We inadvertently had the bulk of the boat perched on an underwater sand bloody dune! As the tide dropped we sank further into the sand until we gently rolled on to our side.
We were deceived by the Navionics chart and the sonar on the boat!
Moral of the story, the Navionics android app is not infallible. We should have trusted the Garmin (also with Navionics) in this case even though it does not show as much detail as the Navionics app. The Garmin was showing the area as an “undefined area” and we would have been more cautious. Thinking we were only moving 2 miles from our previous anchorage, we weren’t as thorough as we should have been.
We thank our lucky stars that we were on a nice sandy bed and not a coral reef in the Caribbean which could have caused serious damage. It all happened so fast, in the space of a few minutes we had gently and elegantly slid on to our side.
We are putting this down on paper to help those who sail realise shit happens when you least expect it. I know we are going to get a lot of “advice” from sailors everywhere, even the armchair ones but maybe this event helps someone somewhere……..
Even an old fart like Captain Mike (turns 60 in 2 days) is never too old to learn a new lesson when living on the water.
Take care out there!
Captain Mike and Nikki.