Here is the great apologist Father Mateo's take:
"After His death, Christ's soul, which was separated from His body,
descended into the underworld." This dogma of our Faith was defined
by the Fourth Lateran Council in 1215. The 5th century version of
the Apostles' Creed contains the article: "He descended into hell."
By "hell" or "underworld" in this context, we understand not the hell
of the damned, but "the place of detention for the souls of the just
of the pre-Christian era" (Ott, p. 191).
Pertinent Scripture texts are: Acts 2:24, 2:31; 1st Peter 3:19-20.
Among early Christian writers who teach Christ's descent after death
into the underworld are: Justin, Irenaeus, Ignatius of Antioch,
Tertullian, Hippolytus, and Augustine.
Thomas Aquinas (S. Th. III, 52, 5) teaches that Christ's purpose in
the underworld was to free the just there by the application of the
fruits of the Redemption.
You see him reference Ott, who is Ludwig Ott, the author of Fundamentals of Catholic Dogma, which is the book used in good seminaries to teach Catholics the faith. It is very orthodox.