Step by step recipe:

1. 1 min.
   Filter 300 ml sea water to strain out any little impurities it might contain.
2. 3 min.
   Pour the sea water into the food processor bowl, add 125 g leaven and mix briefly.
3. 10 min.
   Add 500 g plain white flour (French Type 65) then ½ teaspoon yeast and knead for 5 minutes on minimum speed (1), then for a further 5 minutes on speed 2.
   
   You could also chech the dough by trying the window-pane test.
4. 10 min.
   Tip the dough into a large clean bowl and cover with a plastic sheet. Leave to rest for 10 minutes.
5. 
   At the end of this resting time, take a wooden spatula or a dough cutter and lift the dough, stretching it upwards...
6. 2 hours
   ...then fold it over on itself.
   
   Give a quarter turn to the bowl and repeat the operation. Continue like this until the bowl has made at least one complete turn. In French this kneading manœuvre is called a "rabat".
   
   Cover the bowl again and leave to rest in a warm place for 20 minutes.
   
   This sequence of "rabat" + 20 minutes resting should be done 3 times.
   
   Note: The "rabat" technique is rather hard to describe, so you can watch it in the video on the right.
7. 1 min.
   Cover the bowl and leave to rest in a warm place for 2 hours.
   
   After resting, tip the dough out onto your worktop.
8. 2 min.
   Shape it into a nice round ball by folding the edge under until the top becomes a smooth dome.
9. 2 hours
   Put this ball into a banneton (rising basket), dust with flour, cover and leave in a warm place for 1½ to 2 hours.
10. 40 min.
    Preheat the oven to 240°C (460°F).
    
    Turn the loaf out of the basket, slash the top and bake for 30 to 40 minutes.
    
    Note: As when baking any bread, you should ensure that the oven is filled with steam for the first 15 minutes of baking. This page shows you how; it really is the secret of golden-brown, crusty loaves..
11. 
    When the loaf comes out of the oven, see how crunchy the crust is and how light the loaf is inside.