Baptism is a sacrament of Initiation. The action of Baptism is washing with water, while saying, "I baptise you in the name of the father and of the son and of the holy spirit.
Bible references
Mark 1. 9-11 The Baptism Of Jesus Romans 6. 3-4 Dying And Rising With Christ
Water in baptism represents the identification of the Christian with the death, burial and resurrection of Jesus Christ.
The oil rubbed on the breast of the child to strengthen and prepare for the fight ahead.
During the baptismal ceremony, the godparents hold a baptismal candle that goes home as a memento for the baptized person.
The white garment represents putting on Christ. It is a sign of becoming a new creation, clothed with Christ.
The cross is a symbol of baptism because it is made on your head with the oil when you are baptised