Depends on what denomination you ask/adhere to.

Some thing a water baptism is required. I personally find no basis for this.

While I do encourage water baptism, ultimately it's just a physical ritual and outward expression of ones faith.

Acts 2:38

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.

Matthew 3:11

I indeed baptize you with water unto repentance, but He who is coming after me is mightier than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and fire.

Clearly the Holy Spirit is given only after baptism. I believe true baptism is a spiritual thing as indicated in the Matthew verse. However, as earlier stated water baptism is encouraged as a proclamation of that faith and rebirth in the presence of witnesses. Though I do not think the water is required.