Why does I Pet 3:21 says water baptism doeth also now save us when Jesus saves (Is 43:11) when He baptizes us with the Holy Ghost  (Jn 1:33)?

What the hell are you talking about?

 1 Peter 3:21  NLT   " And that water is a picture  of Baptism , which now SAVES you , not by removing  DIRT  from your body , but  as a response  from God , from a clean conscience  . It is effective  because  of the resurrection of Jesus Christ "  

WHY  provide a reason  purpose or  cause  for a statement of a PERSON  or action

a person could speculate by evaluation  and observation of  human actions and speech INTENT  and association   WHY  that the author held such a BELIEF and found it advantageous to his social status and standing  as a leader   a  desires to PROMOTE such a PROPOSITION 

  a BELIEF is a persons conviction of a PROPOSITION ( promotion ) WITHOUT  supportive EVIDENCE and associated with Emotions  sometimes prejudice  beliefs  are generated  by self experience experiments reflection  generalizations  externally generated beliefs  are  influenced by experts authority and  CANONS

  BELIEF is not a FACT

the TEST for a FACT is demonstrability   To date   promotion of God(s)  Baptism  nor resurrection has been demonstrated independently of  peoples claims  A FACT is a irrefutable piece of information , something that can be PROVEN , unlike a BELIEF

BELIEF  is a THOUGHT  that a person has decided is true  , but does not have to be  a FACT FACTS  are  verifiable

an OPINION is a judgement  based on facts  an attempt to draw a reasonable conclusion

  an OPINION is  potentially changeable  depending on the evidence and interpretation

A BELIEF is a conviction based on CULTURAL or PERSONAL FAITH and values   

the ISSUE may actually be to inquire  as to BAPTISM  SAVES  a PERSON from WHAT ACTION /  EVENT and perpetrated by WHOM 

what parts of that answer  is demonstrable to make it a FACT  or    more of  PEOPLES AUTHORITARIANISM and the use of the a god proposition  to  give   people STATUS  of  leadership CAUSE I SAID SO  and  i   get to be authoritarian  cause i claim a god proposition  TOLD ME SO  = I AM SPECIAL and what ever i say to Be accepted as TRUE

Baptism by immersion is a necessary part of salvation, just as Jesus' sacrifice and atonement are.

I understand water does not save us but what about Lifesavers, are they relevant in salvation, and if so what color would you suggest?

And when you save a document, does that mean it’s been baptized?

Because the ordinance of baptism "washes away sins", Acts 22:16, Acts 2:38, AND put one "In Christ", Gal. 3:27.  C.f. Col. 2:12, Rom. 6:1-5,

Impatience, confusion, lack of faith and ignorance often make it impossible for some people to recognize signs and/or power. 

Both your statements are incorrect. Keep studying. 

None of it matters, Norine.