Lets look at this section of 1st Peter.
so that He might bring us to God, having been put to death in the flesh, but made alive in the [n]spirit;19 in [o]which also He went and made proclamation to the spirits now in prison,20 who once were disobedient, when the patience of God kept waiting in the days of Noah, during the construction of the ark, in which a few, that is, eight persons, were brought safely through the [p]water.21 Corresponding to that, baptism now saves you—not the removal of dirt from the flesh, but an appeal to God [q]for a good conscience—through the resurrection of Jesus Christ,
Lets look closely at how Christ made the proclamation. v18
in the [n]spirit
Remember also the word "now" in verse 19. This means they were not in prison at the time of the proclamation.
Lets look at the context of 1st Peter to understand what he is saying of the Spirit of Christ
chapter 1
10 As to this salvation, the prophets who prophesied of the grace that would come to you made careful searches and inquiries,11 [h]seeking to know what person or time the Spirit of Christ within them was indicating as He predicted the sufferings of Christ and the glories [i]to follow.12 It was revealed to them that they were not serving themselves, but you, in these things which now have been announced to you through those who preached the gospel to you by the Holy Spirit sent from heaven—things into which angels long to [j]look.
Christ proclaimed His Gospel to all men who heard the prophets, and to all who hear us today, because we proclaim it through the power of the Spirit of Christ.
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As for baptism, notice how the baptism relates to salvation.
By appeal, and good conscience.
And what is the connection?
The resurrection of Christ.
Notice also the separation from the physical act.
See how the water that baptized Noah and his family is separate from the Spirit Baptism that is through Christ.