Not the Hydrographer's Passage

Serendipity
David Caukill
Sun 30 Jun 2013 10:53

Sunday 30th  June, Mackay, Qld Australia)   21:06.733S  149:13.6E 

Today’s Blog by David (Time zone BST +9.00; UTC +10.00)

 

The conventional passage into Mackay from the Coral Sea is through the Hydrographer’s Passage. This is a well-documented pass through the Great Barrier Reef, and is lit so that, in principle, it can be used at night.   While it is not a route I have ever followed, it is evident from the chart that it involves a significant thrash SSE into the prevailing SE winds for over 30 miles – if you time it with the flood tide, the wind kicks up an uncomfortable short chop which can be severe at springs.   However, it is the only charted passage into Mackay. A couple of World ARC yachts were badly shaken up there and damaged by the chop in 2012 .  They Oyster World Rally fleet faced similar challenges in 2013.

 

At anchor in Luganville, Vanuatu, I met a yachtsman that regularly sails to the islands from Mackay. He provided me with the waypoints shared among other yachties which define a route to cross the reef about 45 miles south of Hydrographer’s Passage. The course is never less than 206M – a reach in the prevailing winds - and saves about 60 miles on the overall journey to Mackay. Also with the prevailing SE winds across the course there should be no chop on the flood (but I am told there can be on the ebb).  It was worth exploring.  I record the details here for my future edification – if not for yours.

 

.  The key waypoints are:

 

20:15.5S  151:00.2E          Start of Alternative Passage

 

20:22.0S   150:52.0E

 

20:32.7S  150:43.2E          The Bridge

 

20:39.7S  150:37.8E          Clearing Point ( through two charted rocks)

 

20:44.5S  150:29.0E          Back in Charted water

 

Although the charts for this area are not detailed - and for some areas unsurveyed – checking it out on Google Earth gave me the confidence to try it.   We used this passage in June 2013.  We timed our arrival to arrive in daylight at the Start at Low Water Creal Reef/Bugatti Reef; it was shortly after springs; the range for the flood was 2.0 metres.  We set our autopilot to follow the track of the route determined from those way points – i.e. the autopilot adjusted for the tidal set to ensure we followed the ground track defined by these waypoints.

 

We carried the flood right through the reef, which was a good thing because, at the pinch point about half a mile after what I have called “The Bridge” above,  we had 6-7 knots of current with us for about a mile. So although the pass itself (from the Start to the Clearing Point) is about 32 miles long we were through it in 3.5 hours – a beam reach all the way.

 

We transited the reef with an observed least depth on the passage of more than 12 metres (actual depth - i.e. not adjusted to remove height of tide). There are a few patches where the depth shelves sharply (e.g. from 40 to 15 metres) where tidal rips disturbed the surface considerably causing us to exercise considerable caution with a man in the rigging. The shallowest was just after The Bridge where it shelved to 12 metres – otherwise the depths were in the range 26-50+ metres .

 

There are no lights – and very little breaking water over shoals which can be used to fix your position save at 1.5 miles or more range. While it is quite possible that there were dangers/shallows lurking around us we had good light from behind and we did not see any shallow water nearby. However, this not a route I would undertake without good light and one which I would not want to do against the ebb tide (mind you I wouldn’t want do Hydrographer’s against a strong ebb either!). However, in the right conditions, it is a route I would use again.

 

I pass this on because it was shared with us and we used it successfully.

 

Whether you choose to use it is entirely your decision. There are no charts; you are relying solely on essentially word of mouth backed up by whatever comfort you draw from Google Earth. We found the Google Earth pictures were  consistent with our experience.  Entirely your choice and your decision.