Assuming you have a suitable waterway guide, the biggest problem you are likely to have in knowing where you are on the narrow canals is the odd bridge having lost its number. However, as you move onto bigger waterways, it becomes more difficult.
Some waterways (such as the Yorkshire Ouse) have numbered beacons along the banks, while larger CRT waterways are now provided with kilometre posts, which are invaluable, as long as you have a chart that shows them. On wider waterways, like the Humber or the Severn Estuary, the channel is marked by buoys or light floats, red to port and green to starboard as you head inland (lateral marks), as well as other buoys marking hazards. At night, bankside beacons and floating marks may be lit with red, green, yellow or white lights and individual marks may be recognisable by the lights flashing in a particular pattern.
Navigation marks are shown on charts of the area 1. These range from Admiralty charts for larger waterways, to charts produced by the port authority and charts for more inland waters produced specifically for the pleasure boater 2.
If you are venturing onto any freight waterway, especially tideways, make sure you have a suitable guidebook or chart and know what the symbols mean, before setting out. On more maritime waterways, you may find it worthwhile to purchase or borrow a GPS (Global Positioning System) navigator to give you the extra confidence of knowing exactly where you are, especially if visibility becomes poor during your voyage. Hand held GPS receivers, which show your position to better than ±10 metres using satellite signals, are now widely available and are invaluable if you plan to get into the saltier extremities of the waterway system. Knowing exactly where you are is important if you need to call for help - even well inland, such as on the Trent tideway.