One is what you said. The other is the so-called "harrowing" to which Peter alludes and about which there is a very fine description in the apocryphal Acts of Pilate.
I don't know much about it, but I have read that Hans Urs von Balthasar is thought by people who know more than I (a LARGE group) to be wrong in saying that in Hell IHS suffered the extreme alienation from God which is the ultimate effect of sin.
Personally I think that as IHS conquered death by suffering it, it is not so outrageous to think that He harrowed Hell by entering into it fully, so I see no conflict.
Very interesting concept.