Jesus and the Apostles are very united on this. Baptism is required and is not a symbol.
In Acts 8 we see the Eunuch believed in Jesus, yet he still had to be baptized.
Acts 8:36 As they traveled along the road they came to some water, and the eunuch said, "Look, there is water. What is to prevent my being baptized?" ( The oldest and best manuscripts of Acts omit this verse, which is a Western text reading: "And Philip said, "If you believe with all your heart, you may.' And he said in reply, "I believe that Jesus Christ is the Son of God.' ") 38 Then he ordered the chariot to stop, and Philip and the eunuch both went down into the water, and he baptized him. 39 When they came out of the water, the Spirit of the Lord snatched Philip away, and the eunuch saw him no more, but continued on his way rejoicing.
Mark 16:16 He that believeth and is baptized, shall be saved: but he that believeth not shall be condemned.
1Peter 3:20 Which had been some time incredulous, when they waited for the patience of God in the days of Noe, when the ark was a building: wherein a few, that is, eight souls, were saved by water. 21 Whereunto baptism being of the like form, now saveth you also: not the putting away of the filth of the flesh, but the examination of a good conscience towards God by the resurrection of Jesus Christ.
Ezechiel 36:25 "Then I will sprinkle clean water on you, and you will be clean; I will cleanse you from all your filthiness and from all your idols. 26 "Moreover, I will give you a new heart and put a new spirit within you; and I will remove the heart of stone from your flesh and give you a heart of flesh.. 27 "I will put My Spirit within you and cause you to walk in My statutes, and you will be careful to observe My ordinances.
Acts 2:38 But Peter said to them: Do penance, and be baptized every one of you in the name of Jesus Christ, for the remission of your sins: and you shall receive the gift of the Holy Ghost.
Acts 22:16 And now why tarriest thou? Rise up, and be baptized, and wash away thy sins, invoking his name.
1Corinthians 12:13 For in one Spirit were we all baptized into one body, whether Jews or Gentiles, whether bond or free; and in one Spirit we have all been made to drink.
John 3:5 Jesus answered, "Amen, amen, I say to you, no one can enter the kingdom of God without being born of water and Spirit.
I can not find 1 verse that says you can be saved without being Baptized.