It is a complete bath in which every part of the body is washed. The symbolism is that of being laid in the grave of Christ. Our identity and union with Christ is pictured in baptism. An interesting side note is that recent first century excavations of early churches reveal that many baptistries were built in the form of one of two shapes - either that of a grave or of a womb. Many new believers come with a history of old behaviors and activities.
Baptism provides a mile marker from which history begins all over.
Either phrase may be used at a baptism. Baptism shows that we have participated in the death and resurrection of Christ. We WERE baptized WITH Him and risen WITH him, past tense. This brings us to the practical implications of the act, the ethics of baptism. Baptism is to effect one's present life as he seeks to live in faith and obedience to the Lord.