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The Scilly Islands- New Grimsby Sound

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Courtesy Flag

Flag, Red Ensign


None Given


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

No anchoring in St Mary’s Pool or inshore at New & Old Grimsby. 3kt speed limit in St Mary’s Pool



Tidal Data Times & Range

HW St Mary’s is HW Dover – 0630. MHWS 5.7m MHWN 4.3m MLWN 2.0m MLWS 0.7m There is a tidal stream diagram included with the charts of the Islands.

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General Description

Main coverage of the Scilly Isles  HERE

New Grimsby Sound lies between Tresco and Bryher and is a deep water anchorage well sheltered from the East and West but awful in SSE & NNW winds.  For strong Easterlies it is better sheltered than St Mary’s. It is accessible at all states of the tide from the North but only for about a couple of hours either side of HW if entry is made from the South.



If you are familiar with the Islands and coming from the North,.....

.... New Grimsby Sound would be an ideal initial entrance to the Islands but be aware there is nothing in the way of navigation marks (apart from the lighthouse on Round Island) to assist your entrance and in conditions of wind over tide the seas around the North of the archipelago can be very confused. 

If you are just shifting anchorage from the Southern side of the Scillies and want an afternoon’s sail then the trip round to New Grimsby is a couple of hours west about or three hours East about around St Martin’s;  the alternative is to go through one of the Sounds to the east of Tresco. Approaching from the West or NW there are no hazards, the coast is steep to but you may find the sight of the seas crashing against the exposed west side of the islands a little scary; once round Shipman Head at the North end of Bryher just identify Cromwell’s Castle and make for that and the anchorage/moorings South of it.  If you are coming round from the East, Round Island (with its lighthouse) and the double pinnacle of Men-a-vaur will be easily identified and Shipman Head and the North end of Bryher will slowly open ahead. 

Avoid the temptation to head straight for the North end of Tresco from abeam Men-a-vaur, stay north of the transit between Round Island Lighthouse and Men-a-vaur until you can see well into New Grimsby Sound from the NW. This will clear the rocks around Kettle Bottom if they are not already obvious with the seas breaking over them. It’s best to veer over to the deeper water on the West side of the Sound until clear of Gimble point before making for the anchorage/moorings.

The approach from St Mary’s looks daunting but, in fact, if you make the approach at states of the tide suitable for your draft it is fairly simple (Half tide upwards is best).  Remember also that, unlike the waters you may have travelled from, the water here is gin clear you’ll see underwater hazards well before they are under your bow. 

As you pick your delicate way around the “hazards” you will be embarrassed to be overtaken by the ferries virtually straight lining it from St Mary’s to Bryher; don’t be, they draw hardly any water and, having been doing it for generations, know where all the rocks are, to the inch!!   During your stay at St Mary’s you will have identified the lead in marks to the passage clearing Bacon Ledge and the Cow as you leave St Mary’s and, once clear of those rocks, can shape a course for Samson Hill on Bryher until you identify Nut rock which you leave well to Port. Pick up the perches on Hulman and Little Rag Ledge.  Give the Hulman 30m offing and the Little Rag a good 100m offing. By this time the tide should be well enough advanced for you to head straight across Tresco flats (ignoring the dotted line on the chart) for the gap between Plumb Island and Merrick Island.  You should be able to see the Hangman (well into the Sound) as you pass the Little Rag Ledge and if you keep this in line with Merrick island on about 340T until Appletree Point is abaft the beam you’ll be well clear of the off-lying rocks there.

Of course if you are deep draft and working the limits of the tide then you should veer round to the West after passing the Little Rag Ledge. Head for the left hand of Samson Hill’s two summits until Yellow rock is abaft the beam on about 230T and then turn back NE for Tresco, taking care to clear Lubber’s Rock and Plump rocks on the way in.  Detailed descriptions of the land marks on this part of the approach can be found in Martin Fishwick’s Cruising Companion.

One word of caution here, the tidal streams in the Sound are quite strong (up to 2kts at springs) and change directions four times (as opposed to the normal two) in the tidal cycle. You need to be aware of this when anchoring.  It is prohibited to dry out close in to Tresco and you should avoid anchoring so as to interfere with the ferries into and out of New Grimsby Quay.  You will be charged for anchoring as well as mooring to a visitors buoy.

Berthing, Mooring & Anchoring

Once clewed up and either anchored or moored in the Sound....

.... you will have access to both Tresco and Bryher and would be advised to avail yourself of the deal for a third night free on the mooring if you pay for two in advance.  It now costs £20 per night for the normal buoys but if you need to use one of the two big yellow buoys at the North end of the trots, they are £30. They charge £5 per night just to anchor. 


It will take you a day and a picnic lunch to explore Bryher and a comfortable day to visit Tresco Gardens leaving a day to explore the North of Tresco. Limited provisions can be obtained at New Grimsby and, if you time your run ashore until after the first helo of the morning, the morning paper! (but you'll have to wait until 2019 for that when they start the new helicopter service) The delights of Tresco have to be explored to be appreciated; they range from a posh (and expensive) hotel above Old Grimsby to the busy New Inn pub at New Grimsby (where you can arrange for a shower if you need one) and there is a post office and some interesting shops.

Water is available at the quay and if you ask the harbour master, Henry Birch, (tel 07778601237) he will be able to get hold of petrol and diesel (in cans) and even arrange for your dhobi to be done. Back in the early nineties local information was that one could get a shower at the Island Hotel at Old Grimsby but it was found that, to do this, one had to take a room for 24 hours so the tap at Old Grimsby had to suffice!!  These days, if you ask at the bar of the New Inn at New Grimsby, you should be able to get a shower there. A visit to Tresco is not complete without a wander around the Tresco gardens; they are every bit as exceptional as the literature claims so give yourself plenty of time to explore them and if you are an horticulturist you might even need two days!! 

Don’t forget also that there are regular ferries over to St Mary’s so you can avoid the hugger-mugger of St Mary’s Pool and use them instead (the return fare is £12.00 per adult for 2021)



Your Ratings & Comments

Summer 2021
Written by chalky | 9th Jun 2021
The ‘three nights for the price of two’ has been stopped. The overnight price for a mooring is still £20
Written by Don Thomson | 3rd May 2018
No changes but we understand that the helicopter service will be reinstated in 2019
Update Spring 2016
Written by dononshytalk | 12th May 2016
These notes were reviewed by Don in May 2016. No changes, not even the prices. There are rumours that the helicopter flights may be resumed either this summer or next but we think they are still at the "talking" stage
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