Wash the watercress three times and lightly salt it; let it sit overnight in a strainer.
The next day, combine all ingredients in a bowl squeezing with your hands as you mix.
Pack ingredients in quart jars, leaving about ½ inch of room at the top.
Let sit on the counter to ferment for 3-5 days with the lid loosened to let air out as it ferments.
Keep stored in the fridge.
