Before you reach the portal

A tunnel is one of the most memorable things you will do on the inland waterways. It is also the place where a little preparation pays off more than anywhere else on the network. A narrow, unlit bore concentrates the mind, so treat the approach as part of the passage rather than a pause before it.

• Read the notices at the portal. They give the tunnel's length, headroom, whether it is one-way, whether traffic lights or a tunnel keeper control passage, and the hours of operation. Photograph the sign so you can check it later.
• Bring the boat's air draft down. Take off the chimney, lower any tall aerial, and stow the cratch board or pram cover frame if there is any doubt. Most tunnels are lower than the bridges you have been passing under.
• Brief the crew. Everyone should know who is steering, where the torches are, and that nobody stands on the roof, the gunwales or the bow. Keep feet and hands inside the boat.
• Check the engine, fuel and batteries before you commit. Turning back inside a tunnel is difficult to impossible, so you want to be confident the boat will keep running.

Lighting: see and be seen

A forward-facing tunnel lamp is essential, and it needs to be working before you reach the entrance, not switched on hopefully in the darkness. Aim the beam slightly forward and up so it shows you the walls and the water ahead rather than bouncing straight back at you.

• Run your navigation lights as normal. A white light at the stern matters just as much as the one at the bow, because it tells any boat following you exactly where you are.
• Carry a head torch as well as a handheld torch, and keep spare batteries in a dry place. A head torch leaves both hands free on the tiller.
• Put a light on inside the cabin, particularly if crew are below. It keeps morale up and makes the boat easier to spot from another helm.
• Resist the temptation to fit a searchlight. An overpowering beam blinds oncoming boaters and washes out your own view of the wall.

Horn signals and one-way tunnels

Sound one long blast on the horn before you enter, and listen hard for an answering blast. A reply means somebody is already inside, or is about to come the other way, and you should hold back at the portal until the tunnel is clear. Keep the signal short and single, especially near houses or moored boats where a prolonged blast at six in the morning will not make you popular.

Many of the longer tunnels are one-way and controlled, either by traffic lights or by a tunnel keeper who records your boat name, gives you a safety briefing and sends boats through in convoys. Obey the lights without argument, never enter against a red, and if you are in a convoy keep a sensible gap so the boat ahead does not feel crowded.

Steering through the darkness

Once inside, hold the centre of the channel and steer with small, calm movements. Your wash bounces off both walls and pushes the stern around, so keep the throttle low — enough for steerage, no more. Sudden bursts of power are what send boats scraping down the brickwork.

• Keep a steady distance from the boat in front, ideally a good few boat lengths. If they stop, you need room to stop too.
• Look ahead for ledges, protruding bricks, low sections of roof and drips that will land on your neck.
• Keep ventilation open up top even in the wet. Exhaust fumes have nowhere to go in a tunnel, so never let anyone sit in a closed stern or breathe the engine's output.
• Swap helms only where the tunnel is wide enough to do it safely, and ideally not at all.

Meeting other boats and dealing with problems

Where a tunnel is wide enough for two boats, keep to the right and pass port to port, slowing right down as you do. Where it is single file, one of you will need to wait — usually whoever has the least room or the shorter distance to go. Signals in tunnels are limited, so slow, clear movement speaks louder than any gesture.

If you break down, get the boat hard against one wall, put someone at the stern with a torch to warn approaching traffic, and sound the horn. Long tunnels often have emergency points and phones marked along the route, and a passing boat can carry a message out if you have no signal. In the event of fire or smoke, get everyone off the boat and out of the tunnel immediately. Never swim, however shallow the water looks.

Coming back into the light

Exit is a moment to be ready, not to relax. Your eyes take a minute to adjust, and there is often a moored boat, a bend or a bit of crosswind waiting just beyond the portal. Keep the speed low until you are clear and can see properly in both directions.

• Refit the chimney once it has cooled and the boat is clear — not while it is still hot from the flue.
• Check the roof for anything dislodged and the hull for any new scrapes worth noting.
• Thank the tunnel keeper if there is one, and log the passage in your notes with the time and direction.

Tunnels reward patience. Go in prepared, go in slowly, and the blackness turns from something to fear into a genuinely stirring bit of boating you will want to do again.