“Oh my! Whatever happened?”

The small boy looked at me, his brown eyes wide with astonishment, obviously envisaging some cataclysmic disaster, as I recovered Black Swan one evening. I was about to say that I had been away all day and was unaware of any catastrophe occurring at Cobnor, when I realised he was referring to the water level.

“The water was right up to this bank this morning — where’s it all gone?”

I explained that all was well; that the tide comes in and goes out twice every day, and one little boy went home wiser, hopefully, than when he came out. However, I’ve noticed from snippets of conversation at various times that even fellow dinghy cruisers don’t understand the full implications of tide heights. Take spring tides for example. Most sailing folk know that spring tides come higher than neaps, and that the currents are swifter. I expect that many, and in fact I did myself when I started cruising, choose to sail at spring tides to make launching easier and to use the currents to make a faster passage. But do they realise in fact they are taking a greater risk and making things difficult for themselves?

Why?

Because with spring tides the current flows much faster, wind against tide conditions make the sea much rougher. Even in force 4, conditions can be surprisingly unpleasant, particularly round exposed headlands. In an ideal world we will have a following wind and a fair tide and make a fast passage, but how often do things go according to plan when we are sailing? If the tide turns against us when we have a following wind, the sea will get rougher and progress will slow dramatically, if the wind is light the sea will be calm enough, but we might find we are sailing backwards over the ground. With a headwind, progress against a 3 knot tide is nil unless we have a powerful engine to help.

The other hazard is that saltings, behind which it is possible to shelter at neaps, are covered at high water springs. Launching and recovery also becomes difficult at the top of a spring tide when all the beach or launching ramp has disappeared and the only place to leave your boat is bumping against a concrete wall.

Trying once in a big spring ebb to beat between the moorings in Itchenor fairway I lost the wind and got swept, at 3 knots onto the mooring wire of a large yacht; result — a nasty slit in my foredeck.

Neap tides are altogether friendlier. It is usually possible to progress, even when the tide has turned against you. Wind against tide conditions are not nearly so frightening, and on the ebb there is less risk of accidental grounding because the water is dropping more slowly. In some creeks which dry right out at springs, it is possible to remain afloat at neaps. If the wind gets too much at neaps and it becomes necessary to land, there is a good chance of some dry beach between your boat and a hard sea wall, even at the top of the tide; altogether more reassuring.

Another fact of which some people may be unaware is that spring and neap tides always occur at the same time of day, respectively, in a particular area. For example at Chichester, the highest spring tide is always at midday and midnight, and neap high tides are always in the early morning and early evening, around 7 o’clock. On the other hand at Falmouth, spring high tide is always at 6 o’clock and low tide at midday.

If I have no tide tables handy and I want to know the time of high water, I can get a pretty good idea from the state of the moon. If there is a new or a full moon, I know high tide will be about 11 o’clock on my stretch of the coast, so if I want to walk on the sand I must go down to the sea in the early evening. If it is a half moon, here in East Sussex where I live there will not be any sand because the sand below our shingle beach only uncovers at springs. If you can’t see the moon look in your diary; almost any diary will give you the moon’s phases; it doesn’t need to be a yachting one.

Of course things are not always so simple. There are the big equinoctial spring tides in spring and autumn. In between we have exceptionally slack neaps. On some days the water hardly seems to move at all. Offset against these we have in the summer months, spring tides which are not much bigger than neaps, and big neaps which are nearly as high as springs. Consult your tide tables when planning a cruise, they will give you the heights as well as the times of high and low water. The greater the height the faster the currents will run.

Don’t forget, although a big favourable tide and following wind will give a fast passage and a splendid sail, spring tides will give you the most trouble when things go wrong.