Start with the Water, Not Just the Weather

Most of us check the forecast first, and that is entirely reasonable, but on the British coast the tide will often decide whether a passage is pleasant or punishing. Two boats can leave the same harbour an hour apart on the same breezy day and have completely different afternoons: one beats gently to windward, the other slams into a short, steep sea with spray flying over the coachroof. The difference is nearly always the state of the tide and the direction of the stream.

Before any coastal sail, spend fifteen minutes with the tide tables, a tidal stream atlas and a chart of your intended route. That quarter of an hour will repay you tenfold in comfort, and every so often in safety.

Reading a Tide Table Properly

Tide tables give high and low water times and heights for a standard port, plus corrections for secondary harbours. Those corrections matter: the difference between the reference port and your own can be half an hour in time and a metre in height. A few practical points to keep in mind:

• Check the date and the time zone. British tables are usually in UT or BST, and mixing the two up is a classic early-season error.
• Note the range, not just the times. The difference between high and low water tells you how much water will move and how fast it will run.
• Apply the rule of twelfths. In the first hour after low water, one-twelfth of the range has come in; two-twelfths in the second hour; three in the third and fourth; then two, then one. The middle hours of the flood and ebb are when the stream runs hardest.
• Do not guess your depth. If you draw 1.8 metres, allow at least a metre under the keel in settled conditions, and more if any swell is running into a shallow bay.

Springs, Neaps and the Size of the Range

Spring tides arrive roughly a day or two after a full or new moon, and neap tides about a week later. On a big spring range in somewhere like the Bristol Channel or the Solent, streams can run at two or three knots, and in narrow channels considerably more. That is the day to plan your passage with the tide, not against it. On a neap you get more slack and more forgiveness, but also less water over the shallows and sills, so check the charted depths again before you commit to a shortcut.

Wind Against Tide: The Chop Maker

This is the single most useful thing to understand. When wind blows against the tidal stream, the sea builds into a steep, short, uncomfortable chop with almost no wavelength. When wind and stream run the same way, the sea lies down and you can make good progress even in a fresh breeze.

So compare your forecast wind direction with the stream direction on each leg of the route. If the two oppose each other, expect a bumpy ride through the middle hours of the tide, and either change your timing, shorten the exposed leg, or accept it with a reef in and the kettle on. Places with a reputation — the races off headlands, narrow straits, estuary mouths — are worth avoiding altogether at the wrong state of tide.

Local Hazards and the Notes That Save You

Every stretch of British coast has its own character. Before you go, study the chart and the pilotage notes for:

• Overfalls and races off headlands, where the stream accelerates around a point and stands up in a rough sea.
• Bars and estuary entrances, which can be dangerous with an onshore wind on a strong ebb and are often only passable near high water.
• Tidal gates such as harbour sills, lock entrances and marina cills, which open for a defined window either side of high water.
• Ferry routes and commercial traffic, plus firing ranges and separation schemes that may close an area to small craft.
• Pot buoys and floating lines, best avoided in poor light and around the top of the tide.

Local sailing clubs and harbour offices are generous with advice if you ring ahead, and a harbour master will always prefer a call to a shout.

Building the Plan at the Kitchen Table

Lay out the chart, the almanac and the forecast, then work backwards from your arrival. Choose a departure time that puts the strongest stream under your keel on the longest leg. Write down tidal heights and stream directions for each hour of the passage so you can check your progress against them, and mark the bail-out harbours along the way — the ones you could reach if the wind pipes up or someone aboard starts to feel unwell.

Leave your plan with someone ashore, carry a means of calling for help, and keep a listening watch. Check the tide, check the wind against it, and you will not only arrive safely — you will arrive smiling.