It represents everything!
The water is nothing special, there’s no magic involved. You don’t guarantee heaven by being baptized. Baptism is simply how a new follower of Jesus, commonly called a Christian, shares with the world what he/she has chosen to believe and publicly identify with Jesus!
Jesus did it too!
Even Jesus got baptized, and used it to demonstrate how we, too, can share in the victory Jesus won in his death and resurrection!