More than once I’ve sworn never to cruise through the Kiel Canal again, always after a seemingly endless stretch negotiated in foul weather or in an underpowered yacht. But when the weather plays ball and if time is on your side, a passage through the Kiel Canal can be one of the most interesting parts of a voyage to or from the Baltic.

Moored in front of the Gieselau-side lock gates or at anchor in the idyllic lake of Flemhude before Kiel, it is hard to believe the Kiel Canal – aka the North Sea-Baltic-Canal or Nord-Ostsee-Kanal (NOK) in German – is the world’s busiest shipping route. In total some 43,000 ships and around 20,000 or so private yachts go through the canal every year.

The idea for a canal to link the North and Baltic Seas came up in the Danish-German war of 1864. Otto von Bismarck recognised that a waterway would allow German ships to slip between seas undisturbed by Danish cannons. However, his contemporaries were not quite so visionary and planning did not begin in earnest until 1878, when Emperor Wilhelm I finally approved a vast budget of 156 million Goldmark. Just as impressive is that the huge project came in within budget.

In the end, it was Wilhelm II who finally opened the Kaiser-Wilhelm-Kanal, as it was then called, in 1895. The second Wilhelm (half-English, incidentally) was partial to his racing yachts, so the canal was useful for more than warships. It helped establish Kiel Week, also founded by Wilhelm II, by considerably improving access to the Baltic for international yachts.

Indeed, the Kiel Canal has always been a door to the east for foreign sailors. Frank Mulville transited with his family on Transcur in 1967. As he writes in his book Terschelling Sands: ‘We started motoring down the canal after a very expensive lunch at a restaurant near the jetty, keeping well into the side out of the way of the stream of ships. The banks of the canal soon became wooded and rural, with occasional vistas over the countryside of Schleswig-Holstein, which was a pleasant agricultural land – not unlike parts of Essex.

‘The volume and diversity of the shipping was extraordinary. The boys soon devised a game of guessing the nationality of passing ships and Patrick drew up a complicated scoring sheet. There were tankers and freighters from 20,000 tons downwards as well as small German, Dutch and Danish coasters. Sometimes we were unable to identify the ensigns even with the aid of the almanac – countries like Kathiri, Gabon, Dahomey and Chad defied identification.’

It can seem like nothing has changed. I have been through the canal many times, but the transits that linger in my mind are those slow passages made on hot summer days. Once or twice I have dropped anchor at a wider section and dived overboard to cool off in the peculiar, brackish water. Much of the canal is too narrow for this and sailing is not allowed, but you can motorsail if there is a good following breeze.

Given the canal’s length of just over 50 nautical miles, you can cover it in a long day of motoring; yachts are restricted to daylight hours only. But it is better to split up the trip and stop for a night at one of the permitted berths. The most peaceful are: off the Gieselau Lock at 40.5km; in Lake Obereider (entrance off 66km); Lake Borgstedt (67.5km and 70km); and in Lake Flemhude (85.4km). Kilometres are counted from west to east, from Brunsbüttel to Kiel and clearly marked ashore.

An extract from a Yachting World feature, May 2014