In my opinion, between His death and resurrection, Jesus went and made a proclamation of His victory on the cross to those fallen angels who were being held in prison. But since there is no definitive answer on this, I am open to further discussion on it.
Verse 18 does not require the interpretation that Jesus did not rise physically. In fact, logically speaking, if we held to the "spirit only" idea of His resurrection, we would have a contradiction with other verses in the Bible; namely, John 2:19-21 and Luke 24:39 cited above. Since John 2:19 clearly teaches that the temple of Christ's body was raised, 1 Pet. 3:18, which has different interpretations among scholars, cannot be held in a way that would contradict other, clearer scriptures such as John 2:19-21 and Luke 24:39).
Furthermore, different Bibles translate verse 18 differently. Some say Jesus was "made alive by the Spirit" (KJV, NKJV, NIV, MLB) while others say "...made alive in the spirit" (NASB, NEB, RSV, JB, and the 1901 ASV). It is certainly possible that Jesus was made alive by the Holy Spirit which is consistent with the Trinitarian aspect of Jesus' resurrection where God raised Jesus (1 Thess. 1:10), the Father raised Jesus (Gal. 1:1), and Jesus raised Himself (John 2:19-21), and the Holy Spirit was also involved in His resurrection (Rom. 8:11). It is also accurate to say that Jesus was raised in the spirit in that His spiritual body, which is His physical glorified body, was quickened, made alive, became real as the first fruits of all creation (1 Cor. 15:20).