The word baptism in its origins is Greek and means "immersion" and "bath." Immersion in water is a sign of death and emersion out of the water means new life. To bathe in water is also to undergo cleansing. Saint Paul sums up this truth when he says, "You were buried with him in baptism, in which you were also raised with him through faith in the power of God, who raised him from the dead" (Col 2:12).
(Source: USCCB)