To those who think that faith alone saves them, Paul says otherwise. He said beleif in the heart that God rasied Jesus from the dead justifies, whereas confession, or acknowledgement, with the mouth that Jesus is lord saves. Water baptism is outward acknowledgment that Jesus is lord. So we can conclude from this that verses in which only faith is mentioned are referring to faith that both believes and acts.
That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. Romans 10:9-10