Did Jesus descend into hell in his living body?
The short answer is no.
Some Creeds say ”Christ descended to the dead” (Descensus Christi ad Inferos) without interpreting the words meaning.
Christ, in his human soul united to his divine person, went down to the realm of the dead. He opened Heaven's gates for the just who had gone before him.
Jesus did not actually go into Hell as what the word generally means. The word Hell in Latin is infernus, infernum, or inferni and simply means the lower regions. The term in Hebrew is Sheol and in Greek, Hades.
633 Scripture calls the abode of the dead, to which the dead Christ went down, "hell" - Sheol in Hebrew or Hades in Greek - because those who are there are deprived of the vision of God. Such is the case for all the dead, whether evil or righteous, while they await the Redeemer: which does not mean that their lot is identical, as Jesus shows through the parable of the poor man Lazarus who was received into "Abraham's bosom": "It is precisely these holy souls, who awaited their Savior in Abraham's bosom, whom Christ the Lord delivered when he descended into hell." Jesus did not descend into hell to deliver the damned, nor to destroy the hell of damnation, but to free the just who had gone before him.
There is an ancient homily on the subject, of unknown authorship, usually entitled The Lord's Descent into Hell that is the second reading at the Office of Readings on Holy Saturday in the Catholic Church.
The Catechism of the Catholic Church states: "By the expression 'He descended into Hell', the Apostles' Creed confesses that Jesus did really die and through his death for us conquered death and the devil 'who has the power of death'. In his human soul united to his divine person, the dead Christ went down to the realm of the dead. He opened Heaven's gates for the just who had gone before him."
This is clearly expressed by St. Thomas Aquinas in his Summa Theologiae:
Whether Christ went down into the hell of the lost?
A thing is said to be in a place in two ways. First of all, through its effect, and in this way Christ descended into each of the hells, but in different manner. For going down into the hell of the lost He wrought this effect, that by descending thither He put them to shame for their unbelief and wickedness: but to them who were detained in Purgatory He gave hope of attaining to glory: while upon the holy Fathers detained in hell solely on account of original sin, He shed the light of glory everlasting.
In another way a thing is said to be in a place through its essence: and in this way Christ's soul descended only into that part of hell wherein the just were detained. So that He visited them "in place," according to His soul, whom He visited "interiorly by grace," according to His Godhead. Accordingly, while remaining in one part of hell, He wrought this effect in a measure in every part of hell, just as while suffering in one part of the earth He delivered the whole world by His Passion.
As for 1 Peter 3:18-20, the Douay-Rheims clearly implies that Christ visited in the Spirit and not in the flesh. Translation is the key to this:
18 It was thus that Christ died as a ransom, paid once for all, on behalf of our sins, he the innocent for us the guilty, so as to present us in God’s sight. In his mortal nature he was done to death, but endowed with fresh life in his spirit, 19 and it was in his spirit that he went and preached to the spirits who lay in prison. 20 Long before, they had refused belief, hoping that God would be patient with them, in the days of Noe. That ark which Noe was then building, in which a few souls, eight in all, found refuge as they passed through the waves.
18 Quia et Christus semel pro peccatis nostris mortuus est, justus pro injustis, ut nos offerret Deo, mortificatus quidem carne, vivificatus autem spiritu. 19 In quo et his, qui in carcere erant, spiritibus veniens prædicavit: 20 qui increduli fuerant aliquando, quando exspectabant Dei patientiam in diebus Noë, cum fabricaretur arca: in qua pauci, id est octo animæ, salvæ factæ sunt per aquam.
18 ὅτι καὶ Χριστὸς ἅπαξ περὶ ἁμαρτιῶν ἔπαθεν δίκαιος ὑπὲρ ἀδίκων, ἵνα ὑμᾶς προσαγάγῃ τῷ θεῷ, θανατωθεὶς μὲν σαρκὶ ζῳοποιηθεὶς δὲ πνεύματι: 19 ἐν ᾧ καὶ τοῖς ἐν φυλακῇ πνεύμασιν πορευθεὶς ἐκήρυξεν, 20 ἀπειθήσασίν ποτε ὅτε ἀπεξεδέχετο ἡ τοῦ θεοῦ μακροθυμία ἐν ἡμέραις Νῶε κατασκευαζομένης κιβωτοῦ, εἰς ἣν ὀλίγοι, τοῦτ' ἔστιν ὀκτὼ ψυχαί, διεσώθησαν δι' ὕδατος.