It was recently announced that the Plage des Sables Blancs in Tréboul will be the site of an open water swimming marathon on July 15th and 16th 2017.
they hope to attract 150-200 swimmers who will compete over several distances 1, 2, 2.5 and 5km.

For more information check out http://www.letelegramme.fr/finistere/douarnenez/nage-en-eau-libre-grand-rendez-vous-en-juillet-aux-sables-blancs-04-01-2017-11351660.php