What do Jehovah’s Witnesses teach about water baptism and is baptism by full water immersion essential to salvation? This question has arisen from answers to a question I recently asked about the Lutheran Church and what they teach about salvation (they call it justification) and whether or not they think water baptism is essential to salvation.  A comment was left suggesting that Lutherans, Presbyterians, most Reformed Protestants and Catholics promote infant baptism and that they recognize the baptisms of other Trinitarian denominations.

However, Baptists and Jehovah’s Witnesses reject infant baptism and advocate full water immersion of adults who fully understand what they are doing and what baptism means.  Many Catholics and Protestants who become Jehovah’s Witnesses have already been baptised (sprinkling) as infants.  What is the official position of the organisation – do they then have to undergo full water immersion in order to be accepted and recognised as Jehovah’s Witnesses? 

After a period of intensive study with a U.K. Baptist church, I was baptised by full water immersion as an adult “in the name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19). The U.K. Baptist Church has never believed that baptism is essential to salvation.  Neither does their baptism mean you have become “a Baptist”.  Rather, baptism is understood as an outward symbol of having come to saving faith in Christ Jesus.  If I now wanted to become a Jehovah’s Witness would I have to be re-baptised, or would my earlier baptism be valid? I ask because of what I read in the Watchtower Study Edition April 2017 article ‘What You Vow Pay’:


  “11 Have you dedicated your life to Jehovah and symbolized your dedication by water baptism? If so, that is wonderful! Recall that on your baptism day, before eyewitnesses, you were asked whether you had dedicated yourself to Jehovah and understood that “your dedication and baptism identify you as one of Jehovah’s Witnesses in association with God’s spirit-directed organization.” Your affirmative answers served as a public declaration of your unreserved dedication and showed that you were qualified for baptism as an ordained minister of Jehovah. You must have made Jehovah very happy!  Source: https://www.jw.org/en/library/magazines/watchtower-study-april-2017/what-you-vow-pay/


To sum up: Do Jehovah’s Witnesses believe adult water baptism (full immersion) is essential to salvation, and would they recognise the baptism of a person from another denomination who wanted to become a Jehovah’s Witness as valid or would they have to be re-baptised?  This question is not about “right or wrong” but is seeking clarification on how Jehovah’s Witnesses view baptism in relation to salvation.
You are correct  that Jehovah’s Witnesses reject infant baptism.
We believe a person must be old enough to be a disciple. A disciple is a learner or taught one. Baptism is meaningless unless one is old enough to be a disciple. (Matt.28:19-20)
We also teach that full immersion is necessary to follow the manner in which our exemplar Jesus was baptized. In fact the Greek words translated baptize or baptism refer to immersing,dipping, or plunging under the water.
As far as the part of your question about a previous baptism in another religion being valid for Jehovah’s Witnesses, the answer is no.
Being baptized as one of Jehovah’s Witnesses is preceded by an extensive teaching program and a person will have to demonstrate that they have a basic understanding of bible teachings, live in harmony with them and give an affirmative response to the question “ Do you really want to be one of Jehovah’s Witnesses?”
Additionally there are over 100 other questions that are discussed to ascertain that a person meets the scriptural requirements for baptism.
Also as you point out in your question on the day of a new JWs baptism they answer yes to the question do you recognize that  “your dedication and baptism identify you as one of Jehovah’s Witnesses in association with God’s spirit-directed organization.?”
Is baptism essential for salvation?
It is expected that a person who “comes to an accurate knowledge of Jehovah and the one He sent  forth Jesus Christ” would be moved to dedicate their lives to Jehovah and symbolize it by being baptized.
Still we understand that baptism itself is not what saves. Salvation is possible only because God’s Son died a sacrificial death and was resurrected.
Added to that is the requirement to maintain a good conscience before God by continuing to conform to His standards.
Baptism only saves us if we remain faithful as witnesses of Jehovah.
More info here