The romantic inspiration for Marseille's annual Défi de Monte Cristo (Monte Cristo Challenge) is, as the name hints, Alexandre Dumas' 1844 novel, The Count of Monte Cristo.
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Its hero, Edmond Dantès, escapes from the impregnable Château d'If - where he has been unjustly sentenced to life imprisonment - by swimming to freedom.
Hundreds of swimmers flock to Marseille every year to pay homage to him in an annual race from the island-fortress to the shore.
Created in 1999, it has become one of the most important sea swimming events in the annual calendar. The dates for the 2015 Monte Cristo Challenge were 20 and 21 June.
However, the race doesn't replicate the exact conditions of Dantès' swim in the book. He makes for the islands of Tiboulen and Maïre - having first struggled his way out of a body bag (you'll have to read The Count of Monte Cristo to find out just why).
Thankfully, contestants in the Monte Cristo Challenge aren't required to perform the same feat.
The route, too, is different from that in the novel. It begins on the northern shore of the If island, goes towards the Soudaras lighthouse and continues towards Endoume point.
It then passes for 300 metres / 328 yards along the Corniche JF Kennedy, in front of the Anse de la Fausse Monnaie and La Plage du Prophète.
The race ends at the Plage du Grand Roucas Blanc in the Prado beach park just south of Marseille, where there's a pop-up village, the Village du Défi. This is the best spot to watch the race as a spectator.
The race is five km / three miles long, but there are shorter races too throughout the weekend. A purse of 3,000 €uros awaits the male and female winners of the main race and each entrant gets a souvenir T-shirt.
And don't worry if you're not in the race: there's plenty of action on land too. In 2015 there were two discos at the Village du Défi, on the evenings of 19 and 20 June, with DJs and live music.
How to Enter the Monte Cristo Challenge
You can enrol for the race in early February on the Monte Cristo Challenge website (the form can be downloaded on the site). You can swim either with or without flippers: until recently there was a single race with a handicap for flipper-wearers but now, in order to accommodate more swimmers, the Challenge consists of two separate races.
Still, it's highly advisable not to delay, as places are very limited and in the past (as with the equally iconic Marseille-Cassis half-marathon in the autumn) these have been snapped up instantly.
In fact such was the demand in 2014 that the website crashed, forcing the organisers to extend the enrolment period. And even so, all the spots were subscribed to within a few hours. In 2015 a record number of 2,500 swimmers participated in the various events.
Taking up the Monte Cristo Challenge costs 37€; the shorter races are cheaper and are limited to 300 entrants. The Junior Challenge, open to swimmers aged 12-15, is free.
This being France, all contestants must be in possession of a recent medical certificate attesting to their fitness.
Bear in mind that the Monte Cristo challenge is at the mercy of local weather conditions. In 2013 the race had to be cancelled because of very high winds, and it was touch and go again in 2015 (though in the end the event did go ahead as planned).
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The Count of Monte Cristo by Alexandre Dumas père, pictured.