For many people, reaching the sea each summer is a national obsession. For landlocked countries, not having a coastline can be a national trauma.
Take the Czech Republic, a country whose historical borders once stretched as far as the Adriatic, but which is now stranded in the middle of Europe.
There the sea exerts a powerful, almost mesmerising force, inspiring many amateur seafarers and adventurers.
In a shed behind a church in a small town called Nymburk, 420km (260 miles) from the nearest sea, two Czech adventurers are building a boat. It doesn't look like much. It certainly doesn't look like it will float. At least not yet.
Hundreds of plastic bottles have been sealed, pumped full of dry ice - for extra buoyancy - and strapped to a 10m (33ft) wooden frame.
The pedals have been ripped out of a pair of old bikes and attached to a rudimentary propeller. Four plastic garden chairs have been bolted to the deck.
A crude cabin is emerging - also made of plastic bottles - to keep off the rain.
"Oh it's a huge challenge," concedes Honza Kara, a tall, 22-year-old student from Nymburk, as he squints down the length of the hull.
"There are lots of people who support us. But there are also lots of people who are convinced we're going to sink after 10 metres. So it'd be worth it just to prove it to them."
He and his fellow mariner, 21-year-old car mechanic Jakub Bures, are entering their final weeks in the boathouse before a planned launch into the River Elbe - known as Labe in Czech - some time at the end of June.
Their plan is to pedal all the way down the Elbe to the great port of Hamburg on the North Sea.
Lure of the sea
They seem rather vague about the details, such as the exact distance - 900km? 850? Or how long it's going to take - a month? two months? For now they are concentrating on the boat's technical specifications; everything else is secondary.
Remarkably they will need no special permit or qualifications. As long as your boat is less than 20m long (66ft) and not powered by either engine or sail, you can float - or pedal - down any navigable river.
The two are no strangers to adventure. Last year Honza walked 3,000km from Nymburk to Gibraltar. Jakub, meanwhile, walked from Nymburk to Prague - a rather more modest 50km - but not so easy when you're walking backwards (he had mirrors fitted to his rucksack).
Honza and Jakub are following in a great Czech tradition of technical ingenuity, often driven by the lure of the sea.
In the 1970s, a Czech economist called Karel Zlabek published an outrageous plan to build a 410km rail tunnel from southern Czechoslovakia under the Alps to the Adriatic, emerging near the port of Koper in present-day Slovenia.
The soil from the excavations would be piled into the sea to produce an artificial island called Adriaport, which would become Czechoslovak territory.
The project was primarily conceived in economic terms - it would have slashed the time and cost of getting freight from the north of Europe to the Mediterranean, bypassing the Alps, or so the planners hoped.
But it was the fact that the underground trains would also carry tourists to the beaches of Yugoslavia that captured the public imagination in Czechoslovakia.
'In our DNA'
It was an especially enticing prospect for a nation that had briefly enjoyed access to the sea.
King Otakar II of Bohemia vastly extended his realm in the 13th Century, reaching as far south as the Italian coastal area of Friuli.
"I think it's something that's present in the DNA of Czechs," said Sandra Baborovska, curator of a tongue-in-cheek art installation at the Prague City Gallery called Return to Adriaport.
"In history we had the sea. We were a rich country with a rich history, with a rich culture. I think we Czechs are not obsessed, but depressed by not having the sea," she told the BBC.
Sadly for Prof Zlabek, Adriaport came to nothing.
After a brief burst of enthusiasm - Communist Czechoslovakia even launched tentative talks with Austria, Italy and Yugoslavia - the idea was shelved.
Rumour has it the Czechoslovaks received an angry phone call from Moscow.
So today the landlocked Czechs wearily board charter flights to Turkey, or load up the car to Croatia.
The Friuli coastline of Bohemia is a short footnote in medieval history. The tunnel to the Adriatic an obscure engineering curiosity.
In fact all that is left of the Czechs' glorious ocean-going past is their word for "Hi!" - the nautical "Ahoj!"
Romantics believe the word was brought back by Czech sailors serving in the Austro-Hungarian Navy.
The truth may be more prosaic. But it is a daily reminder of what might have been, had King Otakar held on to his seashore.