The Rishonim (Medieval Halachic authorities) debate the issue of whether or not the Beracha of "Ha'motzi" recited over bread covers the water that one drinks during the meal. Meaning, if a person drinks water during his meal, must he recite "She'ha'kol" over the water, or has the water been covered by the "Ha'motzi" recited at the beginning of the meal?
According to the view of Rashba in the name of Raavad, even though "Ha'motzi" generally covers foods eaten as part of a meal, it does not include water, which is not ingested for the purpose of satiation like other foods. Other Rishonim, including Rabenu Tam, however, argued that drinking constitutes an integral part of one's meal in that it helps facilitate digestion, and because people generally drink over the course of eating a meal. As such, it is indeed included under the Beracha of "Ha'motzi," and hence one need not recite "She'ha'kol" when he drinks water during a meal.
The Shulchan Aruch in siman 174:7 adopts the second view, exempting one from reciting "She'ha'kol" over water drunk during a meal. He adds, however, that it is preferable to drink some water before beginning a meal, and have in mind that the Beracha of "She'ha'kol" recited over that water exempts all water he will drink during the meal. This way, he ensures that according to all views he need not recite a Beracha when he drinks water during the meal. One who follows this stringency must drink less than a Revi'it of water, for if he drinks a Revi'it his situation becomes subject to a debate among the authorities as to whether he must now recite a Beracha Acharona. (See Mishna Berura, s"k 37.)
It must be emphasized that this is merely a measure of stringency, and not required according to strict Halacha. As mentioned, the Shulchan Aruch explicitly follows the lenient position, that "Ha'motzi" exempts one from reciting "She'ha'kol" over water during the meal. Therefore, one need not exert himself to drink before the meal in order to satisfy all views, but if he has water readily available it is preferred that he drink a small sip before the meal. This is the position as well of the Ben Ish Chai (Rabbi Yosef Chayim of Baghdad, 1833-1909). (See Halichot Olan, Helek 2, page 30.)
With regard to wine drunk during a meal, according to all opinions the Beracha of "Ha'motzi" does not exempt one from reciting "Borei Peri Ha'gefen" over wine, and thus one who drinks wine during a meal must recite a Beracha. It should be noted that the Beracha of "Borei Peri Ha'gefen" covers all beverages drunk subsequently, and hence one need not recite "She'ha'kol" over beverages drunk after he had recited "Borei Peri Ha'gefen." (See Shulchan Aruch, siman 174:1-2)
Summary: According to the accepted view, one need not recite "She'ha'kol" over water drunk during a meal after he recited "Ha'motzi," but he should preferably satisfy all views by drinking a sip of water just before beginning his meal. One who drinks wine during a meal must recite "Borei Peri Ha'gefen." The Beracha of "Borei Peri Ha'gefen" covers all other beverages, and thus after reciting this Beracha one need not recite "She'ha'kol" over beverages drunk subsequently.