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The Scilly Islands-Old Grimsby & St Helen’s Pool

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Courtesy Flag

Flag, Red Ensign


None appropriate


AC 1148 Isles of Scilly to Lands End; 34 Isles of Scilly; 883 Isles of Scilly and the Principal Off-Islands; SC 5603 (8 to 13) Various parts of the Isles of Scilly including small scale Falmouth to Scillies; Imray C7 Falmouth to the Scillies and Trevose Head (insufficient on its own)

Rules & Regulations

See Text



Tidal Data Times & Range

HW St Mary’s is HW Dover – 0630. MHWS 5.7m MHWN 4.3m MLWN 2.0m MLWS 0.7m

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General Description

Main coverage of the Scilly Isles HERE 

This used to be the quieter side of Tresco; the ferries from St Marys all land their passengers at New Grimsby and it is there that the souvenir shops and cafes are to be found. Visitors landing by ferry all make a bee line for Tresco Gardens so the area around Old Grimsby tends to be off the beaten track. 

The only draw back is that you’ll have to walk half a mile over the island to the Post Office for your morning news paper.  In SW winds on a sunny day the beach is a delight but regrettably one is no longer allowed to anchor there and dry out.

They have laid out visitors’ moorings but if you have a shallow draft keel you can anchor closer in which gets you out of the main tidal stream but, regrettably, anchoring close in, inside a line from Long Point to Blockhouse Point, is no longer permitted.


The easiest approach is from the North through Old Grimsby Sound.

 As with New Grimsby Sound there are no navigation marks to assist with the approach apart from the lighthouse on Round Island but that at least will be a starting point when trying to differentiate between the various lumps of rocks and islands that you are presented with on a northerly approach. Men-a-Vaur is particularly distinctive with its double/triple pinnacle.  If you are coming round from the NE, once you have cleared Men-a-Vaur do not turn in for Old Grimsby Sound until you have identified and circumnavigated Golden Ball and its associated rocks;  you need to have clear sight of the Sound between Norwethel and Tresco before turning in and even then you must take care to clear Little Kittern.  On our chart we have marked a course which is the absolutely closest you must be to the hazards; we have also highlighted the 57 minute and 58 minute latitudes notation to draw your attention to the change in scale from the chart you have been following from Land’s End to the charts you are now looking at; the distance between Norwethel and Merchants Point is less than a cable.  However, once you have become familiar with the scale of the charts and what you are seeing from the cockpit the charts are beautifully detailed, just make sure your plotter/GPS is on the same chart datum as that you are using at the chart table.  This is one case where, if you have printed and laminated screen captures from the charts on this site during the winter you will be miles ahead of the game.

If you are making the approach from the NW having been in New Grimsby Sound there really isn’t much of a problem, just give the Kettle and Kettle bottom a safe offing and follow the island round into the Sound. On the other hand if you are making a landfall from somewhere like Southern Ireland then you will have to be very careful to accurately identify what you are looking at with your chart, especially as the nearer islands to you will be seen against the background of St Mary’s which is higher and will be sighted before them.

If you want to come in from the South through Crow Sound you will need to do your sums carefully and follow the lead-in marks on the chart. There is an alarming amount of “green stuff” on the charts, especially around Tresco and St Martins; after a few days here you will learn that the tidal range here makes navigation over it (the green stuff) perfectly feasible as long as you choose the right state of the tide to do so.  You will find that after a week’s sailing around these waters your chart will be marked by sight lines you have found useful (as in “when that opens around that, I am clear of that”) and we have thrown in a few on our approach chart to illustrate this. You can see that when the beacon at the West end of St Martins becomes open around Great Cheese rock you will be clear of Tea Ledge and, if you are heading for Saint Helens Pool, you can start shaping your course for there. Simples!! It’s basic transit navigation but you will use it around these islands in a way you have possibly never done before.

Saint Helen’s Pool is best approached from the North East through the Saint Helen’s Gap or from the Hats SCM; again we would suggest you mark sight lines on your chart to aid your progress around areas like Hunters Lump and the Chinks as GPS information is all very well but you are involved in very small cross track errors here so, make very sure of the predicted depth of water and exactly where you are before leaving your departure point. If you look at the photo “Looking over St Helen’s Gap” you’ll get some idea of the scale of things.

Berthing, Mooring & Anchoring

You will be charged here at the same rate as on the other side....

.... in New Grimsby ie. £20 per night on the visitor’s buoys and £5 per night to anchor. The HM doesn’t always come round for these dues and there is an “honesty box” at the pier.  There is no charge for anchoring in St Helen’s Pool


There is a water tap at the landing stage in Old Grimsby harbour and the Island Hotel is prominent (where you would be wise to book if you intend eating there) For anything else you will need to trek across to New Grimsby which, unless it is raining, is not a punishment!  Many years ago one could spend days here and be undisturbed (as most visitors to the islands take one look at the chart and see “’Ere be Dragons”) but nowadays it is a little more populated (as are all the anchorages)


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Written by Don Thomson | 3rd May 2018
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