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Rounding Portland Bill by the 'Inner Passage'

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What is the route?
This is a tidal timer and indicative set of waypoints for rounding the Bill of Portland, or Portland Bill as most mariners call it, at the southern end of the Isle of Portland. A dangerous tidal race, called Portland Race, exists to the south of the Bill that can be so violent as to make it perilous for leisure craft to attempt to pass through it.

The options, therefore, are to pass are either to avoid the Portland Race by ‘passing outside’ of the area, or by taking the 'inside passage' between the Bill and the race. The safest route is always to pass outside of the Portland Race as the Needles to Portland Bill Route location and Portland Bill to Start Point Route location Coastal Overviews set up. This route description and timer describe the other 'Inside Passage' option of passing between the rocks off the end of the Bill and the Race to the south.

Why sail this route?
For a vessel passing between Waymouth or Portland and Lyme Bay, the outer passage will most likely involve several additional hours of additional sailing. In good conditions, neap tides, settled seas, wind and current in accord, the 'inner passage' and with optimal tides the 'Inner Passage' presents no concern and is by far the most optimal approach.

Newcomers should only attempt the 'Inside Passage' in good conditions, with a Neap tide and the benefit of a copy of the Admiralty Tidal Stream Atlas NP257 ‘Approaches to Portland’ for advance planning. Our tide time counter will help set the correct time but cannot be relied upon on its own. The inshore passage requires precise visual pilotage to stand off the shore, maintain transits to identify andy southward drift and avoid lobster pot buoys, so it’s important to choose a date where the tides permit a pass around the Bill in daylight. The inshore passage should never be attempted during Springs, in onshore winds or wind-against-tide conditions of above Beauford force 4.

Tidal overview
Today's summary tidal overview for this route as of Saturday, July 20th at 13:34. The correct selection of tidal streams suitable to take one around the Bill is vital. The ideal time to arrive at the Bill is when the tide has just turned and has started to go your way, be it west or east. At this transition point, the streams are lighter and the race is not in full flow so it is the safest time to take the inside passage and pick up the longest possible following tide to continue up or down the channel. The below tidal counter sets up these timings as presented.
Please note

The current tidal event is springs so expect streams to be at their strongest.


(HW Dover -0100 to +0200)

Starts in 08:49:30

(Sat 22:24 to 01:24)


(HW Dover +0500 to -0500)

Starts in 02:31:30

(Sat 16:06 to 18:31)

What are the navigational notes?
Please use our integrated Navionics chart to appraise the route. Navionics charts feature in premier plotters from B&G, Raymarine, Magellan and are also available on tablets. Clicking the 'Expand to Fullscreen' icon opens a larger viewing area in a new tab.

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Please zoom out (-) if all of the waypoints are not displayed.
The above plots are not precise and are indicative only.


Portland Bill is a narrow promontory (or bill) at the southern end of the Isle of Portland, and the southernmost point of Dorset, England. South of the Bill lies Portland Race in which severe and very dangerous sea states can occur.

Portland Bill lighthouse
Image: Michael Harpur

The race is caused by the convergence of three tidal dynamics that occur close south of the Bill:

  • • Flanking Bay Eddies: Very strong south going currents run for 10 out of 12 hours, along the east and west sides of Portland Peninsula to converge close south of the Bill.

  • • Portland Ledge: This is a shallow ledge that extends 1¼ miles southward of the Bill. A quick look at the chart will show that to the southwest of the Bill the depth steps up from about 60 – 80 metres too from 12 - 5 metres in less than ½ a mile. The main body of the east-west going English Channel streams are forced to ride up over the uneven and shoaling bottom causing turbulent seas.

  • • Strong Tidal Streams: The peninsula compresses the channel tidal streams vastly accelerating their velocity and ferocious tidal stream sets off the Bill during spring tides. Streams attaining 7 knots in the direction of the main current are charted in the tidal atlas and flows of 10 knots have been found in and close by the race.

The result is one of the most dangerous areas of broken water a vessel unwittingly sail into in the English Channel. In heavy weather, especially when the wind is blowing against the current, a severe and very dangerous sea states occurs with irregular steep standing waves and breakers. In an easterly gale, against the body of the flood stream, the whole space between Portland and the Shambles is one sheet of broken water - see below videos. Even in fine weather, the noise caused by the Race may be heard for a considerable distance. Conversely, during neeps with fair winds, the race can be barely perceptible.

In all circumstances, Portland Race should be avoided by small craft. The Race, along with the Shambles sandbank, has made Portland's coast notorious and the area has been littered with shipwrecked vessels down through the centuries. Today the majority of Weymouth lifeboats calls are to rescue yachts that were unaware of the race’s dangers and were unexpectedly swept into the tumult unable to escape.


The dangers of the race can be avoided by using the 'Inside Passage'. Here the current is slightly weaker being closer to the shore and the main body of the stream also shoots clear of the headland, leaving a more manageable area of still water and weak current off the tip of the Bill. It is this area of relatively smooth water, located anywhere between the rocks off the end of the Bill and the Race to the south, that an effective shortcut can be had. The breath of this area can be anything from 200 metres wide to ¾ of a mile because the race moves around depending on tidal conditions. Depths here are excellent from 4 to 16 metres and there are no outliers.

Portland Bill's inside passage
Image: © Marc Bryans

Before attempting the 'inshore route' it is advised that precautions are taken for the event of being accidentally pushed down into the race. Everything should be squared away below decks, all hatches closed and that all crew are in heavy weather gear with lifejackets and harnesses clipped on. A tow rope should be made ready in case it may need to be called for. The engine should be running, on standby or for motor sailing, but maintain a lookout. One of the primary hazards of the area are its numerous lobster pot buoys that are sometimes sub-surface because they are dragged under by the current.

If in any doubt over the conditions call Portland MCI, who overlook the location, on P: +44 1305 860 178, 7 am to 7 pm daily during the season. They also maintain a VHF 16 watch.


The best time for eastbound vessels is at the three hours of slack water commencing at HW Dover +0500 where it is possible to use the passage up until HW Dover -0500 (HW Portland -0300 to 0000). Correct timing is essential to prevent the yacht being set down into the Race.

Chesil Cove make a good tide wait location for eastbound vessels
Image: Gareth James via CC BY-SA 2.00

Vessels that arrive too early for the tide gate should tuck into West Bay and wait for the tide to turn. If there is any concern of arriving too late alter course in good time to go south of the Portland Race and the Shambles and take the outside passage.

If timing is correct close in on the Chesil Beach to the north of Isle of Portland, so as not to be swept south into the race by the currents running out of West Bay. Then keep close to Chesil Beach and follow the south-going stream keeping 250 metres off the shoreline all the way around. The waypoints provided are indicative only as this cut is all about eyeball navigation.

Passing round the 'Bill'
Image: mike george via CC BY 2.00

Some rough water may be encountered abeam of the Bill but the roughest water is most likely to occur off to one side or the other. There is ample water beyond 100 metres of the daymark on the Bill and the inshore smooth is usually a 400 metres wide. A local rule of thumb is to approach the Bill close enough for a boy on the rocks to hit you with a pebble and that is the sweetest spot. This is a matter of personal comfort as the currents here are strong but there is no inshore set and the primary concern is being pushed southward into the race.

A strong countercurrent will be encountered setting down the east sides of the Isle of Portland once the Bill has been rounded. Likewise in certain conditions, some rough water can be experienced at Grove Point located on the east side of the peninsula, 2½ miles northeast of Portland Bill Light and readily identifiable by its conspicuous coast guard station.

The key to the ‘inside passage’ is vigilance and to be constantly observing shoreline transits to make certain the vessel is not being pushed southward into the race.


The converse timing for westbound vessels is to arrive at the Bill from HW Dover -1 to +2 (HW Portland +4 to HW -6). The ideal time to depart Weymouth or Portland Marina is about an hour earlier, HW Dover -2 (HW Portland +3), making use of a favourable southerly stream along the east side of the Bill to carry the vessel down.

Portland Bill's stone beacon with a westbound yacht
Image: Jim Champion
The best point of approach for vessels passing westward up the channel is to come in close beneath Grove Point on the eastern side of the peninsula, so as not to be swept south into the race by the currents running along the east side of Portland Peninsula. There is the conspicuous Grove Coastguard station close to Grove Point that helps positively identify it. A drying rock awash at high water lies 100 metres from the shore at Grove Point.

From Grove Point, where overfalls may be seen offshore and to the south, follow the coast about 250 metres from the shore as already described in the above eastbound description. During the prevailing winds, westerly or southwesterly, expect a windless area from the high northern end of the island to about halfway round to the Bill. On its fringes, there will be downdraught gusts.


The complete course is 5.84 miles from the waypoint 'Grove Point' to 'Chesil Cove' tending in a west north westerly direction (reciprocal east south easterly).

Grove Point, 50° 32.930' N, 002° 24.782' W
250 metres east of Grove Point on the 20-metre contour.

       Next waypoint: 0.41 miles, course 192.37°T (reciprocal 12.37°T)

Grove Pier, 50° 32.530' N, 002° 24.920' W
300 metres southeast of Grove Pier on the 20-metre contour.

       Next waypoint: 1.59 miles, course 215.70°T (reciprocal 35.70°T)

Cave Hole, 50° 31.240' N, 002° 26.378' W
200 metres east of Cave Hole close outside the 5-metre contour.

       Next waypoint: 0.86 miles, course 229.31°T (reciprocal 49.31°T)

Portland Bill, 50° 30.680' N, 002° 27.402' W
On the 5-metre contour 200 metres south of the stone obelisk daymark at the southern tip of the Bill.

       Next waypoint: 0.26 miles, course 309.06°T (reciprocal 129.06°T)

Pulpit Rock, 50° 30.844' N, 002° 27.720' W
On the 10-metre contour 200 metres west of Pulpit Rock.

       Next waypoint: 0.49 miles, course 4.31°T (reciprocal 184.31°T)

Old Higher Lighthouse, 50° 31.334' N, 002° 27.662' W
On the 20-metre contour 350 metres west of Old Higher Lighthouse.

       Next waypoint: 1.20 miles, course 4.24°T (reciprocal 184.24°T)

Blacknor Point, 50° 32.525' N, 002° 27.523' W
On the 20-metre contour 200 metres west of Blacknor Point.

       Next waypoint: 1.03 miles, course 6.12°T (reciprocal 186.12°T)

Chesil Cove, 50° 33.550' N, 002° 27.350' W
On the 20-metre contour ¼ of a mile out from the beach at Chesil Cove.


If there is any doubt about the conditions the safest and easiest approach is always to be found by ‘passing outside’, or to seaward of the race and its overfalls. Keep at least three to five miles south of the Bill during calm weather or at least seven miles in bad conditions, especially so during wind-over-tide conditions on a spring tide. The east-going flood to the south of the race is favourable for the best part of 7 hours from HW Dover +6.

Once past the race round up and preferably pass to the east of the dangerous Shambles Bank that lies 2½ miles east of Portland Bill. This irregular shaped bank is marked by west and east cardinal light-buoys on either end. It is also best avoided, as is the gap between it and the Race, as strong tidal streams may cause heavy seas in this entire area. At night the Shambles sandbank is covered by a red sector light from Portland Bill lighthouse.
What is the best sailing time?
May to September is the traditional UK Sailing season with June-July offering the best weather. The amount of bad weather varies quite widely from year to year. The British Isles weather is highly variable because they are islands positioned between the Atlantic Ocean and a large land mass, continental Europe. As a result, the entire area lays under an area where five main air masses meet and alternate:

  • • Tropical Maritime Air Mass - from the Atlantic

  • • Polar Maritime Air Mass - from Greenland

  • • Arctic Maritime Air Mass

  • • Polar Continental Air Mass - from central Europe

  • • Tropical Continental Air Mass - from North Africa

The air masses can come in from any direction bringing with them all types of weather and where they meet they create weather fronts. But as a general rule, the prevailing winds across the British Isles are from the southwest.

Fine summer weather is typically punctuated by the passage of Atlantic depressions bringing periods of strong wind and rain, and sometimes poor visibility. These gales rarely cause surprises as they are usually forecasted well in advance. Good weather windows of 48 hours are easy to predict but any longer than that there's an increasing chance of change. Winters see a predominance of wind and rain.

With thanks to:
Michael Harpur eOceanic

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Weymouth RNLI rescues a yacht trapped in the Portland Race

Portland Race during a storm

Sailing through the 'inner passage'

Tom Cunliffe discusses the 'inner passage'

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