We had a very pleasant, flat and easy downwind sail on the spinnaker yesterday. The only problem is that we were winding our way through an unconscionable number of rocks, reefs, islands and underwater hazards. Geography is a bitch. Like all Tonga, Ha'apai is along a ridge line which stretches north to south. This ridge towers over the surrounding oceanic valleys, never mind the incredibly deep trench just east of here. Sailing the Ha'apai group is like flying past the tippy tops of a mountain range. This mountain range blocks swell and no small fraction of the wind from the east, but it poses its own hazards. Occasional ridge lines stretch out westwards from the main north south line pushing into our path. It's just part of the entire experience that most of these tops are not actually above sea level. Fortunately, the charts are reasonably accurate and shallow spots can generally be spotted from a distance.
We only had a near miss with the sea bottom once. Needless to say, it was an unnerving experience. We were sailing downwind at about 5 knots in gentle winds. The depth was out of the range of our depth sounder, so easily over 500 feet. There were shallows marked off to the starboard and the port but we were threading between two islets so there was reason to be cautious. I was on the helm at the time, of course. These things always seem to happen when I am on the helm. I think the fates do this to give DrC someone to yell at. Doing a horizon scan, I see just ahead an abrupt change in water color that I swear had not been there a moment before. The angle of the sun can make a huge difference in these situations, and this shallow spot just wasn't visible until we were basically on top of it. I shout to the family, glance down and without transition from "no reading", the depth sounder registered 180, plummeted to 70, then 40. The family scrambled on deck, DrC pointing to the starboard. I turn the wheel over as the depth dropped to 20, then 15, then bottomed out at 6 before heading up again. DrC unnecessarily called, "We're over it."
6 on our depth sounder means that there was an uncharted shallow between these islets at a depth of 10 feet. At 10 feet, a coral head can easily grow up into keel grabbing height for our boat, let alone our monohull brethren with their deeper drafts. Jaime patted my back and noted that that was, "Quite a nail biter, Mom." Oh yeah. I was shaking a bit. Turning back, the shallow was obvious for nearly half a mile. Of course. Angle of the sun. For a few moments, I think DrC wanted to tear a strip out of my hide, but then he looked forward and realized the problem. The sea was an unremarkable dark blue in every direction facing forward even though we knew there were additional shallows to port and starboard. It was only looking back that the sea was broken into large puzzle pieces of blues, turquoises, pale greens, and reef tans. Coral heads we had safely passed showed in sharp relief against the shallow sandy bottom while it appeared as though everything ahead was over 600 feet down. By such small graces, I escaped a lecture.
So all I can say is be careful when transiting the Ha'apai group. It is very pretty here, quite remote, and the snorkeling is magnificent. It would also be quite embarrassing for you to get your boat all the way from North and Central America and run the thing aground on the last leg of the journey. We'll try to avoid that little humiliation today for our last hop before heading for Tongatapu. I also think that if the visibility is poor, I'm just going to put DrC on the helm and save myself the stress and bother.
19 56.1S 174 42.8W Haafeva Island, Ha'apai, Kingdom of Tonga
Oct 4 2011 19:00 UTC