OVERVIEW
The great tidal wave from the Atlantic Ocean splits a little to the south of the southwest coast’s Skellig Islands, and sets in two separate paths around the island of Ireland. One part goes to the north, sweeping round the northwest coasts and enters the Irish Sea by the North Channel. The other part goes to the east, rounding Cape Clear to enter the Irish Sea by the South Channel. Seven hours after the separation occurred the two streams flow together again in the vicinity of St. John’s Point, to the south of Strangford Lough.

This presents a unique Irish Sea tidal efficiency for a cruising vessel passing along this section of the coast. Utilising this tidal opportunity a vessel may avail of more than a dozen hours of continuously favourable tidal streams to speed a passage. Or, conversely, potentially endure almost continuous adverse streams by not optimising a departure time.

All that is required is to have St. John's Point central to the passage and take the benefit of the flood tide converging to the point. Then, having taken advantage of the six hours of tide to arrive at the point at high water and half an hour of slack, continue with the benefit of the diverging ebb as it turns to retreat away from St. John's Point. This then provides six hours of a favourable tide for the onward journey.

The tidal oddity can be used for both north and southbound passages. Vessels that can maintain around six knots should be able to make a passage from Belfast Bay to Dublin Bay with a favourable tide all the way.



LISTED WAYPOINTS
The complete course is 87.28 miles from the waypoint 'Bangor Bay' to 'East of Howth' tending in a southerly direction (reciprocal northerly).











PASSAGE NOTES
Vessels approaching from the north, making a southbound passage, should be outside the entrance to Bangor Harbour five hours after high water Dover (Bangor is Dover +0007) to pick up a small shore-hugging back eddy out to Donaghadee Sound. Then use the waypoints as presented.

This tide optimisation works both ways and at the same departure time. Northbound boats should be outside Howth Harbour at the same time, (0430 after high water Dublin) and depart north. A slight variation going north would be to pass inside Ireland’s Eye and inside Lambay Island to avail of the extra speed caused by tide funnelling between landmasses.

What is the best sailing time?

Sailing season for Ireland is May to September, with June and July offering some of the best weather. Nevertheless the incidence of winds up to force seven and above in June and July are on average two days each month. So you may be either held up or having a blast depending on your sailing preferences. Ireland is not subject to persistent fog – statistically complete days of persistent fog occur less than once in a decade.

Are there any security concerns?

Never an issue known to have occurred to a pleasure vessel sailing off the Irish coast.

With thanks to:

Burke Corbett, Gusserane, New Ross, Co. Wexford.