This very simplified account of how tides affect the dinghy cruiser will either be criticised or ignored by the more experienced, as it will contain no news for them. I have, however, encountered people who have done a good deal of inland sailing whose reading of yachting pilot books has made them terrified of venturing into tidal waters, regarding them as something to be tackled only after someone has become expert in everything else. This seems to me to be a mistaken approach. If you become used to them from the start, it becomes natural to live by the tides all the time, as is essential in coastal sailing.

Many elementary books give the simple explanation of how tides are caused by the daily and monthly variations in the pull of the sun and moon. The results as it effects us is a surge of water up beaches and estuaries about every twelve hours and twenty minutes. Every fortnight the tides are higher at high water and lower at low water — spring tides. In between come neap tides, where the rise and fall are less extreme. Every other spring is higher than the ones before and after — every month, that is. At or around the equinox the spring tides are highest of all. Pressure and wind can affect height, but on the whole the local tide tables are very accurate. It will be seen when you examine these tables that springs always come at about the same time of day in any one place. The rise and fall of the tide is much greater in some places than in others. In the Bristol Channel they have forty foot tides. On the Essex coast they are about twelve feet at springs, and in the Solent less. In all places dinghy anchorages are usually out of the channel and thus well aground for about half the time. The tide tends to build up behind bars on its way up estuaries, so that it may not make an appearance in an anchorage up the estuary until two hours or less before high water. Then it may rush in with great turbulence. On the Severn there is a tidal bore, and sometimes also on the Dee. On the Lune it is not regarded as advisable to sail until this first rush has calmed down.

The movement of the tide is a strong current, varying in speed as things slow down towards high water, gathering force again with the ebb, never to be disregarded by any vessel as slow-moving as a cruising dinghy. If you have a good engine you can cheat to some extent, but you should be prepared for any stage of the tide you will encounter. It requires very little arithmetic to work out that a vessel sailing at two or three knots and tacking against a light wind will make progress backwards against a four knot tide. One learns where the current is least, out of the direct flow in midstream, outside bends, close inshore, but one must never forget this constant movement, and what it will be doing later in the day. Take some examples. You may launch off the beach at Thurstaston on the Dee at about high water. The ebb will carry you out even against the prevailing north-westerly, and if it is a fresh breeze and lasts all day you may be able to turn back after an hour or so and sail slowly back against the tide. You will return to an anchorage which is cut off from the shore by sticky mud, but this is mostly not impossible to walk over on this coast. (In Essex this would be a different story: most of the mud there is much too soft to walk on.) Should the wind fade away or change so that it is contrary on the homeward course, there is no hope of getting back on the same tide, unless you time the sail so that you get back before the ebb has got under way. It will be possible to get the boat up to the anchorage about three and a half hours before the next high water, very probably in the dark. After about another hour you should be able to get the boat on to the hard.

This example was of an open anchorage. Further up the gutter at Heswall, there is no water for sailing until less than two hours before high water, and it only lasts until about two and a half hours after. This is typical of sheltered anchorages well up in the further creeks of any estuaries.

Should you enter a strange anchorage when the tide is fairly well up you will not be able to see where you are dropping your anchor. It is essential to be with the boat and watching the bottom on which she is to ground while you can still move her into a place free from hazards if need be. This is an occasion where local advice is useful.

So far I have written only about the rise and fall of water by the shore. Just as important are the tidal streams along the coast. Those do not turn at the same times as high and low water by the shore. Sometimes the times are almost the same, sometimes the difference may be three hours. This is shown in the Tidal Streams Atlases sold by agents for Admiralty charts, and the directions of these streams are fully explained in Admiralty Sailing Directions. There are many variations and hazards: overfalls off headlands, strange tides round islands, and the strength of the stream may carry you along helpless at six knots off the coast of the Lleyn Peninsula, or up the Sound of Jura. There are counter currents along the shore in places. There may be narrows like those in the Menai Straits known as the Swellies, which can only be sensibly negotiated at a certain half hour on each tide. A dinghy cruise uses the tidal streams like a timetable, and everything is worked out beforehand, with alternative programmes according to the winds encountered.

This is all really common sense; just about everything you do in tidal waters is bound to be affected by this regularly and constantly changing movement of the water. How you will swing at anchor, how long a warp you will need, how much depth you have over a shoal at any state of the tide; all these are the things which make coastal cruising interesting. The tides make movement possible on calm days — you can drift twelve miles without any wind at all. After that you will have to go back or anchor so make sure you get into a place where you can safely wait for a few hours if you want to carry on on the next tide. Dinghy cruisers explore a seascape which changes with every hour of the tide, in infinite variety which makes lake sailing very dull by comparison.