It's a baptism WITH the Holy Spirit.
John 3:3 In reply Jesus declared, "I tell you the truth, no one can see the kingdom of God unless he is born again." 4 "How can a man be born when he is old?" Nicodemus asked. "Surely he cannot enter a second time into his mother's womb to be born!"
5 Jesus answered, "I tell you the truth, no one can enter the kingdom of God unless he is born of water and the Spirit. 6 Flesh gives birth to flesh, but the Spirit gives birth to spirit. 7 You should not be surprised at my saying, 'You must be born again.' 8 The wind blows wherever it pleases. You hear its sound, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit." NIV
Acts 8:34 The eunuch asked Philip, "Tell me, please, who is the prophet talking about, himself or someone else?" 35 Then Philip began with that very passage of Scripture and told him the good news about Jesus.
36 As they traveled along the road, they came to some water and the eunuch said, "Look, here is water. Why shouldn't I be baptized?" 38 And he gave orders to stop the chariot. Then both Philip and the eunuch went down into the water and Philip baptized him. 39 When they came up out of the water, the Spirit of the Lord suddenly took Philip away, and the eunuch did not see him again, but went on his way rejoicing. 40 Philip, however, appeared at Azotus and traveled about, preaching the gospel in all the towns until he reached Caesarea. NIV
When you are baptized with water you receive the GIFT that is the Holy Spirit.
Acts 2:37 When the people heard this, they were cut to the heart and said to Peter and the other apostles, "Brothers, what shall we do?" 38 Peter replied, "Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit. 39 The promise is for you and your children and for all who are far offfor all whom the Lord our God will call." NIV