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Dalkey Sound Cut - Dublin to Killiney Bay

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What is the route?
Dalkey Sound resides between the small Dalkey Island and the mainland. As Dalkey Sound cuts about a mile off a passage between Killiney and Dublin bays it is the normal approach used by inshore leisure craft. The sequence of description is south to north.

Why sail this route?
There are three main ways enter the southern side to of Dublin Bay, or for a southbound vessel to connect with the inshore passage which is the preferred route as far as Wicklow.

  • (i) Pass between Dalkey Island and the mainland via Dalkey Island Sound.

  • (ii) Pass between Dalkey Island and the Muglins via Muglins Sound.

  • (iii) Pass outside the Muglins, offshore and in open water.

The Muglins Sound Route location, (ii), has the complication of the foul ground that lies to the northward of Dalkey Island, in particular, the scarcely awash and unmarked Leac Buidhe Rock situated about 200 metres east of Clare Rock.

The much more straightforward offshore route, (iii) detailed in the Dublin Bay to Rosslare Route location Coastal Description, would be the best approach for a newcomer to take at night, with poor visibility or in uncomfortable weather, but it adds miles.

Dalkey Sound (i), although a narrow channel that has unmarked dangers on either side, it is a clear passage with a least depth of eight metres through the fairway. All that is required is to simply keep about 100 metres off the steep-to mainland shoreline to traverse the sound and it is this that makes it the normal route for leisure craft passing along the coast.

Dalkey Island and The Muglins as seen from the south
Photo: jnestorius cc BY-SA 3.0

Favourable tides, however, are critical to pass through Dalkey Sound. Dalkey Sound streams can attain up to 2.5 knots and it is only when these are adverse that leisure craft are best advised to take one of the other two options.

Tidal overview
Today's summary tidal overview for this route as of Wednesday, August 12th at 09:35. In Dalkey Sound and the south part of Dublin Bay the tide turns about half an hour earlier than it does offshore. The northwest going stream begins at Dover -0600 (HW Dublin +0555). The southwest going stream begins at Dover HW (HW Dublin -0030).


(HW Dover +0000 to +0612)


(Tidal flow )

Ends in 01:44:53

(Wed 05:08 to 11:20)


(HW Dover -0600 to +0000)

Starts in 01:55:53

(Wed 11:31 to 17:31)

What are the navigational notes?
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The above plots are not precise and are indicative only.


Dalkey Island resides off Sorrento Point, the southern entrance to Dublin Bay and about two and a half miles southeast of Dún Laoghaire Harbour. The small island is 24 metres high and 600 metres long with a Martello tower on its summit. It lies immediately offshore 200 metres to the east of the mainland leading down to Sorrento Point. The shore of the mainland is steep-to, but the reef that extends up to about ½ a mile north-northwest of the island has straggling outliers on both sides.

A channel, about 230 metres wide, called Dalkey Sound leads between the island and the mainland and it has from 6.8 to 12.6 metres CD of water. It is a narrow passage with unmarked dangers on either side but is clear and safe down the centre for powered vessels.

But the tidal currents are strong through Dalkey Sound and the key to using it is to catch a fair tide, Neap rates attain 1.5 knots, Springs 2.5 knots. In Dalkey Sound and the south part of Dublin Bay the tide turns earlier:

  • • The northwest going stream begins at Dover -0600, HW Dublin +0555

  • • The southwest going stream begins at Dover HW, HW Dublin -0030

Further offshore and in Muglins Sound the tides are as follows:

  • • The north going stream begins at Dover -0530, HW Dublin -0600

  • • The south going stream begins at Dover +0030, HW Dublin HW

A vessel of moderate speed is better off to avoid Dalkey Sound during an adverse tide. During these times the outer channel through Muglins Sound would be better or to pass further offshore.


The complete course is 0.83 miles from the waypoint 'North Approach to Dalkey Sound' to 'South Approach to Dalkey Sound' tending in a south south easterly direction (reciprocal north north westerly).

North Approach to Dalkey Sound, 53° 16.820' N, 006° 5.760' W
This is located 200 metres northwestward of Maiden Rock.

       Next waypoint: 0.44 miles, course 155.14°T (reciprocal 335.14°T)

Middle of Dalkey Sound, 53° 16.420' N, 006° 5.450' W
This waypoint is off Dalkey Island's northwestern point, to the mainland side of a centre channel path.

       Next waypoint: 0.39 miles, course 162.08°T (reciprocal 342.08°T)

South Approach to Dalkey Sound, 53° 16.050' N, 006° 5.250' W
This ¼ southwestward of the Martello Tower on Dalkey Island.


The below-listed waypoints will set up a passage through the sound and provide some guidance. The vast majority of the passage is made utilising eye-ball navigation.

Vessels passing between Dalkey and the mainland should prefer the mainland side keeping about 100 metres off the shoreline. The shore of the mainland is steep-to and all dangers are off the Dalkey Island side. A reef that extends to the northward of the island group has straggling outliers on both sides of it. Favouring the mainland’s steep-to shoreline side of the sound avoids all issues of the dangers.

The single issue with Dalkey Sound are the tides that run strong here. The tides wrap around the Killiney Bay and may be felt abeam on approach or exit south of Sorrento Point. Look out for overfalls caused by the reconnection of tide runs that wrap around the island in this location also. Other than that enjoy the ride.

Southern Approach Vessels approaching from the south will find Killiney Bay to be composed of a shingle beach that is foul along the shoreline. It is best to keep half a mile off where there will be in excess of 10 metres of water. The Frazer Bank resides to the south east of Dalkey Island. With the least depth of 5.3 metres, it presents little issue for a leisure craft.

Align a central path of approach and keep well off the island as Dalkey’s southwest corner is foul. From beneath the islands southern gun battery, a reef extends 50 metres along the island’s western shoreline to about halfway along the coastline to the area of the Martello Tower.

There is a drying rock scarcely awash close to the south of the landing steps near the ruin of the old church. To the north of the steps, another reef with 0.6 metres over it runs out 70 metres from the shore.

Northern Approach Vessels approaching from the north should identify the rocks extending six hundred metres from the northwest ridge of the Island. The leading rock is Maiden Rock, or Carraig Rock, that stands 11 metres high and is always visible. After this, there are several rocks such as Clare Rock and Lamb Island that are all parts of a large ridge extending north-westward from Dalkey Island of which some are only visible at low tide.
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.

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