A water baptism is the symbolism of the old man being cruxified and cleansed and the new man resurrecting with a new life and relationship through Christ. It is a phsyical representation of this fact. A spiritual baptism is when your spirit-man receives the Holy Spirit when you accept Jesus Christ as your Saviour. Your Spririt has been transformed through confession of sin and acceptance of Christ through faith (Romans 10:9, 10). When God created you, your person is made up of a physical flesh, an inner flesh (inner nature), a mind, will, emotions, soul and spirit, in addition to your senses (taste, touch, smell, hearing, sight). That is your makeup, but since we were bron in sin, our spirit needs a renewal. The only way that renewal takes place is through salvation and receipt of the Holy Spirit, whom Jesus stated would dwell and be our Comforter whom would be sent to be with us after He left this earth as a physical presence and ascended to be with the Father.