Select Page

If you are contemplating a cruise through tidal waters and strong currents, then planning your trip carefully in advance is essential to enable you to take advantage of favourable tides rather than constantly fighting against them.

Big tides demand considerable respect and require a greater degree of planning to ensure you don’t allow them to work against you, as well as creating the potential for a confused sea state in wind against tide conditions. However, with careful timing a big tide can also be used to your advantage, either to considerably speed progress towards your destination, or allow you to take useful short cuts if the water level is sufficiently high.

Strong and complex tidal streams are one of the biggest challenges in some parts of the world. For instance spring tides on the south coast of the UK can run at up to four knots, and even stronger rates are possible in parts of northern France and the Channel Islands, as well as around other significant headlands. In places where tides set strongly many displacement craft will need to time their passages for a favourable stream in this area, while planing powerboats will need wind with tide on account of the steep seas generated in wind against tide conditions.

A tidal stream is rarely a uniform mass of water moving at a constant speed in a uniform direction. Instead, it is weaker in shallow water and near the shore, and at its fastest in deep water. The core principles are that the tide runs fastest in deep water, while relief from an adverse stream can be gained in shallow water. In addition the stream in shallow water and in bays will frequently change direction before the main stream – in effect the edges turn first, which can start very early as a back eddy, before the main stream follows in the new direction anything between 30 minutes and as much as three hours later.

Wind and tide effects

The direction of the wind relative to the tidal direction has a significant impact on sea state. If both are flowing in the same general direction, the sea will tend to be flattened out, while wind against tends to produce a short and steep sea that can be very tiring, even if the stream is helping you make progress towards your destination.

Cross tides


In a strong cross tide it’s all too easy to be swept down tide of the rhumb line between your starting point and destination. In an area such as the Solent, between the mainland and islands off the Brittany coast, where distances are very short, GPS can be used to ensure you track in the correct direction. However, there’s also an easy solution for boats without electronic aids: use a hand-bearing compass to keep the mark behind you on a bearing that will lead you to the next mark. It’s very simple and very accurate and if you’re able to line up a couple of marks on shore to that are on the correct bearing you can do it all by sight.

Longer legs, taking more than an hour or so, in which the strength or direction of the tidal stream changes significantly will need a different approach. Here a course to steer calculation, that allows for the net tidal flow you will experience is more efficient than constantly adjusting course as the stream fluctuates.

Tidal races

Tidal races tend to form off headlands, where the tidal rate is accelerated and the sea bed is liable to be very uneven, often with a significant underwater ridge. As a result, it’s possible to get disturbed water even in almost calm conditions and they can be positively dangerous, even to ocean going yachts, in wind against tide conditions in anything more than a moderate breeze.

A race can be avoided by staying a few miles offshore in moderate conditions and more in severe weather, however, the exact distance necessary varies with different headlands – look for the symbols on you chart for overfalls and tide races. It’s also important to consult local pilot books, which will provide more detail about each significant headland and the conditions that can be expected there in different conditions.

In some cases, in good to moderate conditions smoother water often exists very close inshore – this passage is up to half a mile wide, but can reduce to 50-100 metres as the wind increases and may vanish completely in poor conditions. Again pilot guides will indicate whether such an inshore passage is available and, if so, which stages of the tidal cycle the stream will flow in each direction.

A similar situation can arise with sand bars at a harbour entrance. With a strong onshore wind and ebb tide, these have the potential to form dangerous breaking waves in shallow water. In such cases it’s invariably safer to stay at sea in bad weather than it is to risk entering the harbour.

Tidal gates

The speed of an adverse tide at some headlands effectively turns them into tidal gates that you won’t get past unless the stream is flowing in the correct direction. Clearly, a similar situation also exists with bars and harbour entrances and harbours that have restricted tidal access.

If possible, time your passage so that you aim to get to the tidal gate an hour or so before it opens. You’re much more likely to arrive there later than expected, rather than earlier, so this approach maximises the chances of getting through unhindered.

Tidal heights

Be careful when you’re sailing near low water on spring tides as there may be a lot less depth than you expect for an hour or so each side of low water. Pay particular attention to areas that, because they’re never exposed – and are therefore shown on charts as blue, rather than green – can all too easily catch the unwary. Some of these in popular sailing areas may have least depths of only 0.6m below datum well offshore. They are therefore covered by a reasonable depth for maybe 98 per cent of the time, but for an hour or two on a few days once a fortnight will be too shallow for any yacht to pass over.

Distress flares – which flare, how & when to use?

How to use distress flares at sea Flares should be kept in a waterproof container in an easily accessible location such as a...

How to predict wind direction and strength by reading a weather chart

Weather charts, also known as surface pressure or synoptic charts, contain a lot of information that helps weather...

Anchoring – getting it right is not always straightforward

If you can set an anchor correctly with confidence and know your boat will be safe in a secure anchorage, then you can rest...

Safety Equipment Checklist for Boats

Safety Equipment Checklist for Boats   Liferaft line attached The liferaft will not work unless the trigger line is...

VHF DSC radio – how best to communicate at sea

There are many ways to communicate with others at sea. What makes the VHF DSC radio the best form of short range...

Boat electrics

All boat owners should have a basic knowledge of electrics, both to avoid encountering electrical problems at sea and to stand a chance of solving them should they occur.

Galvanic and electrolytic corrosion

Galvanic corrosion is an electrochemical reaction between two or more different metals, in the presence of an electrolyte (note salt water is a good electrolyte).

Gybing a sailing boat

Gybing is the sailing manoeuvre used to change a boat's direction through a following wind. As with the tacking manoeuvre,...

Engine failure at sea – keeping the boat safe

If the engine stops when you are underway, or your have to shut it down when a warning buzzer sounds, you also need to make sure the boat remains safe. It’s important therefore to recognise situations in which the boat would be immediately put in danger if the engine were to fail.

Rudders and steering systems – Part 3

In the third of our three blog articles on rudders and steering systems, we look at how to replace rudder bearings and repair a water-saturated core.

How to ensure your boat is in proper working condition

In this article Eva Tucker from Volvo Penta presents a handy check list of all the things that you need to check regularly in order to make sure that your boat is in a seaworthy condition. Including maintenance, safety gear and electrical checks.

Leaking decks

Leaking decks are perceived as a nuisance by some boat owners, but if leaks are ignored a much more serious situation may well be developing, especially in the case of boats with balsa or plywood deck cores. So deck leaks do need to be investigated and dealt with.

Sailing & Motoring in Fog

Sailing & Motoring in Fog You can only measure the visibility accurately if sailing & motoring in fog when you have...

Steel and Aluminium Hulls

The two metals used for hull construction are steel and aluminium. These are both very strong materials and will last a long time as long as they are cared for, which primarily means protecting steel boats from rust and aluminium boats from electrolytic action.

Repairing a leaking hull-to-deck joint

If you suspect a hull-to-deck joint has failed, then being absolutely sure where the actual leak is occurring is of prime...

Stern gear maintenance

The stern gear of a boat needs to be checked carefully when the boat is ashore as this is something that can only be done when it is out of the water. The same applies for any maintenance and repairs that may need doing, so it is best to check it all over as soon after an end of season lift out as possible.

Sending distress signals

In an emergency situation at sea, it is a top priority is to know how to send and receive emergency radio calls and alert others of your predicament. Likewise, if you receive a distress signal, you must be ready to go to the help of others.

Sterndrive maintenance

Sterndrives are a popular form of propulsion in the powerboat market, but require a fair amount of care and maintenance. The main factors to be aware of are salt water corrosion, lubrication and regular inspection of the bellows, the condition of which is vital to prevent water from entering into the hull.

Peer to Peer yacht charter – How can you monetize your boat?

There is a growing trend in peer to peer yacht charter. How does it work? People already rent rooms, cars and bikes from one...

Points of Sailing

The course on which a boat is sailing can be described by its angle to the wind, not to be confused with its compass...

Sail trimming for cruisers

Sail trimming tips for cruisers. Whether racing or cruising, a well tuned boat will sail faster and tend to heel less than a boat with badly adjusted sails.

Fire prevention on boats

  Fire prevention on boats - common causes of fire: • Smoking below decks • Galley cookers • Build-up of butane or...

How to operate a winch

Winches are drum shaped mechanical devices used to handle halyards, sheets and control lines. One of the important crew...

Man Overboard Drill

How to respond to crew overboard under sail • Keep the MOB in sight • Tack into the heave-to position, do not adjust the...

How to improve a yacht’s upwind performance

There are several ways to improve the upwind performance of a sailing yacht. Read on for some useful tips including headsail reefing, heavy weather jibs and motor sailing.