In John 4:15 a Samaritan woman asks for "this water" that Jesus offers, and later on in 6:34 certain Jews ask for "this bread" offered, again, by Jesus. The parallel is strikingly intentional. Jesus came to his people to provide another exodus for them. He was the rock who followed them through their wilderness wandering (Ex. 17; Num. 20; I Cor. 10:4), pouring out water to drink for all forty years. Likewise he was the manna--the bread of heaven--that sustained Israel for forty years until they came to a land that was settled (Ex. 16:35). More importantly, Jesus comes to the same land for both of them, but the Jews reject him while many Samaritans offer a warm welcome.
The location of each offer made by Jesus is striking too. At the time of offering himself as "this bread" Jesus had just finished miraculously crossing a sea, and John writes it with a very clear "exodus-crossing" motif in mind; then certain Jews cross the sea over to where he could be found, but they don't want what Jesus himself has to offer them--they just want their stomachs filled with bread. When Jesus offers himself as that bread they must eat to be satisfied, they murmur just like their fathers in the Wilderness of Sin (Exod. 16), and they depart from him.
With the Samaritan woman, the location and response to Jesus' offer is different. That encounter occurs at a well, and throughout the Bible encounters at wells often signify bridal imagery of some sort. Jacob, for example, meets Rachel, rolls away the stone-cover on a well, gives her and her flock water to drink, kisses her, and weeps for joy; their marriage followed shortly thereafter (Gen. 29). Likewise Jesus' encounter with the Samaritan woman is laced with bridal imagery too, especially since it is Jacob's well at which the encounter takes place (John 4:6). Only this time, the point is to portray Jesus as the greater Jacob, the greater bridegroom who gives himself as the water that, when drank, wells up to everlasting life (v. 14).
In John's gospel, when Jesus enters the land he visits his own to obtain a bride for himself; but when his own receive him not, he goes to those who are excited to drink the living waters he has to offer. In John's gospel the contrast is not between partaking of "this water" or "this bread," as though only one would suffice for eternal satisfaction. Rather the contrast is between "this water" which can and does satisfy, and that "bread" which the Jews wanted but does not satisfy because it is not bridal food. By rejecting bridal food and drink--food and drink prepared for the promised wedding feast of their Lord--they rejected the wedding invitation altogether. And by rejecting the invitation this way, such examples are given to us to keep us from setting our hearts on evil things as they did.
To this day Jesus freely offers the living waters of baptism welling up to eternal life, but are we willing to drink and feed our flock with the waters he offers? Every week in the liturgy, Jesus spreads a table and offers his own flesh as "true food" and his blood as "true drink" (John 6:55) so that we may abide in him and he in us. But how do we respond to the invitation of his feast? Do we respond by questioning the legitimacy of his words, or do we respond in faith, trusting that he has the words of eternal life (John 6:60-68)?