The Gemara in Chullin (96b) writes “כבוש הרי הוא כמבושל” – pickled food has the same halachic status as if it were cooked. Pickling means soaking a food in a liquid for an extended length of time. The Rosh says that in order for food to attain the halachic status of pickled it must remain in the liquid for twenty-four hours in a row. Removing the food from the liquid that it is soaking in, for even a minute, would restart the clock in regard to pickling (עיין שו”ע יו”ד קה:א).
The Shulchan Aruch (יו”ד קה:א) rules that if the liquid that was being used for the pickling was a very salty liquid, then the time required for pickling is the amount of time it would take to heat up food on a fire. The Kaf Hachaim says that this is eighteen minutes, and the Darkei Teshuva says that the time is six minutes. The Shach (יו”ד קה ס”ק ב) argues with the Shulchan Aruch, and rules that even in a very salty liquid one needs twenty-four hours to do pickling. The Mishna Berura rules like the Shach.
The Rama says that when part of a food is in the liquid and part of the piece remains above the surface, the taste that gets absorbed through the pickling extends even to the part of the food that is above the surface.