Cherbourg to the Channel Islands looks short on the chart and that is exactly why people get it wrong. Guernsey is a little under 57 nautical miles away, Alderney far closer, and a fast yacht could in theory cover the ground in a long morning. But between Cherbourg and the islands sits Cap de la Hague and the Raz Blanchard, the strongest tidal current on the European coast, and the passage is not really about distance at all. It is about tide. Plan the tide and the miles look after themselves.
I have run this passage in both directions in everything from a flat calm to a brisk reach, and the boats that have a relaxed time are always the ones that left Cherbourg at the right minute, not the ones that left when breakfast was finished.
The distances you are working with
A few numbers to anchor the planning.
- Cherbourg to Guernsey (St Peter Port): roughly 56 to 57 nautical miles.
- Cap de la Hague to Alderney: about 10 miles across the top of the Race.
- Alderney to St Peter Port: about 28 miles, much of it through tide-swept water.
- The back-door run south: about 12 miles from the bottom of the Race down to Dielette.
At a typical cruising 6 knots, Guernsey direct is a nine to ten hour day, and that is before you factor in the tide either helping or hindering you. The streams off the cape can run up to around 12 knots at the very biggest tides, so a few knots of fair or foul current makes a far bigger difference to your day than your boat speed does.
Cherbourg is the ideal place to start because it is open at any state of tide and you can wait in flat water behind the breakwater for exactly the right moment. If you have just crossed from England, the arriving in Cherbourg from England guide covers the entrance, the marina and clearing in, all of which you want sorted before you start thinking about the next leg.
The tidal gate is the whole game
Everything west of Cherbourg runs into Cap de la Hague, and the cape is a hard tidal gate. The detail of how the streams behave, the slack times and the inshore versus offshore routes, is worth reading in full in the piece on Cap de la Hague tides, but the headline for passage planning is simple. You time your departure from Cherbourg so you reach the cape near slack water or with the new stream under you, then carry that fair tide on towards the islands.
A common western plan is to leave Cherbourg around HW Dover minus 3 hours 30 minutes, which puts you off the Hague near HW Dover minus 30 minutes, close to the western slack, with the new west-going stream then helping you across. If you are heading for the islands specifically, some sailors prefer to reference St Helier and aim to round the cape about 2 hours 30 minutes before HW St Helier, which sets you up with rising water at the islands.
Whichever reference you use, the principle holds. You do not leave Cherbourg when you feel like it. You leave when the tide tells you to, and you accept that the cape, not your schedule, fixes your departure time. Get it wrong by a couple of hours and you arrive at the Hague with the stream against you, in overfalls, going nowhere.
Wind against tide is the thing that hurts
The Raz Blanchard is a serious piece of water. When a fresh wind blows against several knots of tide, the overfalls build steep and confused, and a small yacht can be stopped or thrown about badly. This is the same gate, the same body of water, as the offshore Alderney Race tidal gates, and the same rule applies. If the wind will be against the stream at peak rate during your window, do not go. Wait for the next tide or the next day.
Visibility matters just as much. The streams set you sideways fast, and a fog bank rolling in off the Channel turns a routine passage into a guessing game. The islands themselves are ringed with rock, so closing them in poor visibility is no joke. Have a plan for fog before you leave, because what to do if fog catches you mid-passage is not something to work out on the day.
Alderney as a stepping stone
You do not have to do Cherbourg to Guernsey in one hop. Alderney sits right at the gate, about 10 miles across the top of the Race, and Braye harbour is an easy landfall in settled weather with visitor moorings. Breaking the passage at Alderney lets you take the cape on one tide, rest, and then take the 28 miles down to Guernsey on the next favourable stream. For a slower boat or a tired crew, that is the sensible plan, and Alderney is a fine place to spend a night.
From Alderney to St Peter Port you are again working tide through the islands, where the streams between the rocks are strong and the channels need attention. It is not open water, so plan that leg with the same care you gave the cape.
The back door to Dielette
If the cape timing does not line up with your day, there is the quieter option of cutting south from the bottom of the Race, about 12 miles, down to Dielette on the west face of the Cotentin. From there you can later cross to the islands on your own schedule. It works in easterlies or gentle northwesterlies in quiet conditions, but Dielette has tidal access constraints, with the workable slack in the bay falling around Cherbourg plus 3 hours, so it is a fair-weather alternative rather than a foul-weather refuge.
Clearing in and the paperwork
One thing that catches people out on this passage is that the Channel Islands are not in the EU and not in the Schengen area, so the formalities run both ways. Coming from Cherbourg you are leaving France and France's customs reach, and arriving in Guernsey or Alderney you clear in with the local authorities, who run their own arrival and customs procedures. Going back the other way you clear back into France, which since Brexit means flying the Q flag and reporting your arrival at a port of entry like Cherbourg.
Have your boat papers, insurance, passports and the boat's VAT evidence to hand for both ends. It is the same folder you would carry for any French landfall, and if you have already worked through the clearing customs when arriving in France by boat routine on the way over from England, you are most of the way there. The islands are an easy place to clear in, but skipping the step is a poor way to start a cruise, and the return into France is the leg where the Gendarmerie Maritime are most likely to take an interest.
My departure-day routine
Before I leave Cherbourg for the islands I settle four things on a card at the chart table:
- The slack water time at Cap de la Hague for the day, and my go and no-go departure times to make it.
- The wind direction and strength forecast for the time I will be at the cape.
- My intended landfall, Alderney or straight to Guernsey, and the tide for the second half if I am going on.
- The fog plan and the bolthole, Dielette or back to Cherbourg, if it goes wrong.
If the wind is against the stream at the cape, I do not sail. That single rule has kept every Cherbourg to islands passage I have made firmly in the easy category. The crossing is short, the islands are lovely, and the only thing standing between you and a gentle day is one tidal gate that demands to be taken seriously. Respect the cape, leave on the tide and not the clock, and the Channel Islands open up as one of the best short cruising grounds within reach of the French coast.
