Baptism became the way God gave us for salvation after the thief on the cross.
It was after the cross, after Jesus rose again, that Jesus said: "He who believes and is baptized will be saved"
Do you believe Jesus?
The verse in Peter very clearly says that baptism does save us.
The like figure whereunto even baptism doth also now save us (KJV)
Baptism, which corresponds to this now saves you (RSV)
baptism, which this prefigured, now saves you (NRSV)
This prefigured baptism, which saves you now.(NAB)
And this water symbolises baptism that now saves you (NIV)
also to which an antitype doth now save us—baptism (YLT)
Baptism, which corresponds to this, now saves you (HCSB)
which also after a true likeness doth now save you, even baptism (ASV)
Baptism, which is like that water, now saves you (GWT)
There is also an antitype which now saves us—baptism (NKJV)
That was a type of the baptism that now saves you (CCB)
Baptism, which is symbolized by that water, now saves you also (ISVNT)
The rest of 1Pet 3:21 explains in what way baptism saves us. To deny that baptism saves us is a clear denial of scripture.
Baptism the the normative way of salvation that God has given us. It is the way he he has told us. Refusal of baptism is disobedience and disbelief.
However God is loving and merciful. We believe he can, and does, provide salvation for those in the circumstances you suggest. Another example would be someone who dies crossing to road while on his way to be baptised. But those are exceptions that God makes, not us.
We do it God's way not our way.