Out onto the Tideway


Heading down onto the tidal Thames can be an intimidating prospect for even the most experienced boater: commercial traffic, powerful currents and a whole array of lights and signals can be a confusing cocktail to the uninitiated.

Narrowboats heading between Limehouse and the start of the Grand Union Canal at Brentford have to negotiate a sixteen mile stretch of the tidal Thames. If you understand what is going on around you, then it's fairly straightforward. If not, things can get confusing and that’s when you end up in trouble.

Handling the tideway:

In terms of navigation, the tideway is a far more complex stretch of water than you are used to inland. It is very important to have a firm grasp of what is going on in order to navigate with confidence.

It is worth remembering that the tidal Thames is one of the most heavily monitored stretches of water in the UK. This is reassuring but it also means you need to work with the Port of London Authority (PLA) and keep them informed of your movements.

During 2008 the PLA has had a number of issues with boats heading from the inland waterways on to the tideway, the main one being that many boats heading from Lime House Basin up to Brentford are not contacting London Vessel Traffic Services (VTS) to inform them of their actions.

Many boaters do not realise that this is actually a legal requirement. London VTS can be contacted either by VHF on Channel 14, or by calling 0208 8550315.

Heading down from Brentford to Limehouse you are not required to inform London VTS, but the PLA would urge you to do so. VTS will then be able to advise you of any potential dangers on the way downstream.

It is less important for boaters travelling between Brentford and the start of the non tidal Thames at Teddington to get in touch, however if it gives you peace of mind, there is no harm in doing so.


One of the main danger areas on the tideway are the bridges and it is very important that you understand the various light signals to ensure you keep out of trouble and out of the way of the big boys.

Three red balls (lights at night) in an inverted triangle above an arch means that this arch is closed to traffic, a flashing white light above an arch means that a large or difficult to manoeuvre craft is in the vicinity of the arch. A slow flash means there is one craft, a quick flash means there are more. Clear traffic arches are marked by two fixed orange lights.

You should always use the arches furthest to starboard. At night an arch with a fixed white light denotes restricted headroom. Bizarrely, this is indicated by a bundle of straw during the day.

It’s well worth getting your arch right in the first place, as changing your mind at the last minute can lead to disaster in strong currents, particularly if the back end slews round. In the worst case (and it does happen) you could get wedged against the bridge. This could lead to a narrowboat inverting.

Tidal Thames top tips

1) Check tide times and try to avoid heading out on a spring tide. Bear in mind that the river often flows at speeds of up to four knots, so if you’re on a narrowboat you may be unable to punch the tide. Plan your trip accordingly.

2) Ensure that you are carrying an anchor and that it is sturdy enough to cope with the increased loads it may come under.

3) A VHF is always a useful addition, and in order to operate one you will need an RYA Certificate of Competence. In the worst case scenario you can use a phone, but this is not ideal.

4) Check with lock keepers at Limehouse, Brentford and Teddington for any safety notices you need to be aware of, lock keepers are also an invaluable source of local knowledge.

In conclusion, the tidal Thames does not have to be an intimidating stretch of water provided you follow the correct protocol and are confident that you understand what is going on.

If in any doubt, don’t be afraid to ask for advice from someone more experienced. For further advice you can go to the Port of London Authority website, or for training tips, contact the RYA on 02380604100.

Click here for more information on starting boating in Narrowboats and information here about the Canal & River Trust