A tidal gate is a point where the tidal currents flow really fast in one direction and then about six hours later just as fast the other way. They are caused by water entering or leaving a basin on the rising and falling tide. If you want to get through a tidal gate, then you need to be in the right place at the right time.
We sailed from Coral Bay on the Coburg Peninsula in the Northern Territories to Darwin and had a chain of three tidal gates that all had to be passed at the correct time. Brain jogging for sailors.
We left Coral Bay in the morning and sailed west along the top of Australia. The wind was as expected and we managed an average of four knots which put us in the Dundas Strait [1] just as the Van Diemen Gulf began to fill late afternoon. The current picked us up and we sailed through between the island and the mainland at seven knots. We kept going long enough to be well inside the gulf before the tide turned and then tried to sail as slowly as possible to lose speed. We were trundling slowly through the night [2] when an Indonesian warship called on the marine radio and asked if we were OK to be overtaken on the port side. No problem with that.
Despite our best efforts too be slow, we were still at the start of the next gate -the Howard Channel – too early so started to work our way slowly in against the tide. With the current against us, we were making about two knots but as the water began to leave the Gulf it picked us up and we sailed out at eight knots [3].
We turned for Darwin and tried to beat the turn of the tide that would work against us. Unfortunately the wind lessened so we went from five knots to four and then three and then two [4]. Finally with a one before the decimal point we put the motor on for the last half hour and one and a half miles.
Once we reached civilization we read about a gentleman who did the whole route with one or two engines on. OK, he spent the night at anchor and we sailed for 37 hours but, maybe we had more fun.