Coastal walks rarely go wrong on the hills. They go wrong at the water's edge, where a beach that was wide open at breakfast is lapping at the cliff by teatime. The good news is that tides are the most predictable thing on the coast. Half an hour with a tide table the night before is usually the difference between a memorable walk and an afternoon spent waiting on the wrong side of a headland.

What follows is the routine to run through before any walk where the sea has a say: which table to use, how to read it, and how to fit your route around the water rather than the other way round.

Start with a tide table for the right place

A tide table for the nearest big port is a useful starting point and a poor finishing one. Tides vary around the coast, and the gap between one stretch of shore and the next can be half an hour or more — enough to matter at a headland. The UK Hydrographic Office publishes free tide predictions online, and harbour authorities, ferry operators and councils often publish local versions. Where a place is a secondary port, tables list a time and height difference to apply against a nearby standard port.

Two checks before you trust any number. First, whether the times are in GMT or BST; an hour's error is exactly the kind that puts you at a pinch point at high water. Second, the date. Tide times shift later by roughly fifty minutes each day, so a table for the wrong day can be out by hours.

Read the heights, not just the times

Times tell you when the water moves; heights tell you how far. A spring tide, falling around the new and full moon, brings the biggest range: low water retreats further out and high water climbs higher up the beach and into coves. Neap tides are gentler. A path that stays dry at neaps can be submerged at springs, even though the high water time looks similar.

The rule of twelfths is worth knowing as a rough guide. Over the six hours between low and high water, the tide moves about one twelfth of its range in the first hour, two in the second, three in the third, three in the fourth, two in the fifth and one in the sixth. That is why the middle of the tide moves fastest, and why a beach empties slowly at first and then all at once.

Read the forecast and the sea together

The Met Office inshore waters forecast gives wind, visibility and sea state in one place, which is more useful than a town forecast for a walk along an exposed shore. Wind direction matters as much as wind speed: an onshore breeze at high water throws spray across a low path, and a strong one makes rocky sections genuinely dangerous.

Pressure affects the tide itself. Low pressure and onshore winds can push water higher than the predicted level; high pressure can hold it lower. That matters when a route has only a small margin. Rain makes rock and clay slippery, and fog on a cliff top turns a familiar path into a navigation exercise. Take a map and compass if visibility is doubtful, and be willing to shorten the day.

Work out where you can get off the path

Before committing to a route, list the ways out. On many coastal paths the sensible plan is not the one with the best views but the one with the most exits.

• Start and finish: check bus times, seasonal ferries and car parks. A ferry that stops running in September changes the shape of your day.
• Escape routes: note every slipway, beach ramp, inland footpath and lane that meets the coast, so you always know how far you are from an exit.
• Pinch points: identify headlands, coves and beach sections that are cut off at high water, and how long the safe window around low water lasts.
• Estuaries: don't cross tidal sand or mud without local knowledge. Channels shift, and a guided crossing or a long detour is the better choice.
• Signal: coverage on remote stretches is patchy. Download offline maps, and tell someone your route and expected return time.

Fit the walk around the water

Once you have the numbers, the route usually designs itself. Suppose low water is at 11:20 and high water at 17:40, and there is a cove you can only pass within a couple of hours of low tide. That puts your window somewhere around 09:30 to 13:00. Work back to a start time and forward to a finish, and be honest about pace — coastal paths take longer than the distance suggests.

1. Write down high and low water for the day, plus the next day if you might be out late.
2. Mark each pinch point and the window around low water when it is passable.
3. Walk the tricky sections early in the day, not at the end when you are tired.
4. Set a turnaround time and keep to it, however good the weather.
5. Note a shorter version of the route in case conditions change.

If you are unsure whether a section is passable, the answer is usually to walk it another day.

Pack for the day you are actually having

Take a paper tide table or a screenshot of one, a map and compass, a headtorch, water and a warm layer even in August — clifftop wind is its own climate. A phone in a dry bag is sensible, and a spare battery is not excessive if your phone is your main navigation aid. If you have a heart, lung or joint condition that could flare up far from help, speak to your GP before planning a long remote section, and don't be shy about turning back.

The last five minutes before you set off

Check the tide table once more against today's date. Look at the forecast for the hours you will actually be walking. Confirm you know where the exits are, and that someone knows your route and your expected return time. In an emergency on the coast, dial 999 and ask for the coastguard; if you cannot describe your position precisely, an app such as what3words will give an accurate location.

Then go. The coast is at its best when the plan underneath the walk is solid, and the tide is the one part of the day you can predict with real confidence. Get that right, and you can spend your attention on the walking itself.

Photo: MLARANDA / Pixabay