Jesus was baptized and told us to be baptized (Matthew 3:13-17, Matthew 28:18-20, Mark 16:15-16). When Jesus rose again, He conquered death for us too. We receive salvation by trusting and believing in Jesus. We demonstrate our trust in Him by being baptized in water. 

Baptism is how you go public with your faith. It shows others that you have been made new and represents your old sinful life being washed clean because of your faith in Jesus.