The Jews ate the old Passover, before the new came.
The Jews circumcised their children, before the circumcision of the heart was available to all.
Only priests stood before God on behalf of the people, until the great High Priest came and made a way for us all to approach the throne of grace directly.
All were fore runners, shadows of the greater thing to come.
John baptised Jews with Water, before Jesus went to heaven and sent the Holy Spirit and baptised the believers in it.
He literally came to prepare the way of the Lord. He wasn't the one to set in place the way of the Lord, He was the last of the prophets before Christ.
But He knew all this was external and calling men to a repentance that depended on mans best efforts.
He could only wash people externally, but one was coming who would wash them internally.
I cannot prove that literal water or even the symbolic use of it is essential for a Christian since the baptism of the Holy Spirit came.
The Jews certainly practiced water baptism, and other jewish traditions but when the gospel hit the gentiles, you have a hard time applying these symbolic things of the hews to them, as James and Paul were pretty much adamant none of it was necessary or beneficial to salvation.
Luke 3:16-17 English Standard Version 2016 (ESV)
John answered them all, saying, “I baptize you with water, but he who is mightier than I is coming, the strap of whose sandals I am not worthy to untie. He will baptize you with the Holy Spirit and fire.
AMP
“As for me, I baptize you with water because of [your] repentance [that is, because you are willing to change your inner self—your old way of thinking, regret your sin and live a changed life], but He (the Messiah) who is coming after me is mightier [more powerful, more noble] than I, whose sandals I am not worthy to remove [even as His slave]; He will baptize you [who truly repent] with the Holy Spirit and [you who remain unrepentant] with fire (judgment).
"Baptism" is indeed necessary, for unless you be born by natural means, and again by the spirit, you are not the Lords. I would say that the "washing of water" is by the word now, the gospel, Jesus, which and whom we receive, and which alone can make us clean.
John 3
3 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
4 Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother's womb, and be born?
5 Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
Jesus equates water here as the natural birth.
That said, it wont hurt anyone to have a splash and profess their faith.