Even though "he descended into Hell" speaks of a descent, it is the first step in the creed toward exaltation. If you look at the creed, it can be very neatly visualized graphically as a big V, painting a picture of Christ's humiliation and then his exaltation.
(Hmm. Due to the nature of this medium the V will be more of a >. You know what I mean.

)
And in -
Jesus Christ, his only Son, our Lord,
... who was conceived by the Holy Spirit
... ... born of the virgin Mary
... ... ... suffered under Pontius Pilate
... ... ... ... was crucified, died and was buried
This is the low point in Christ's humiliation. Then begins the exaltation.
... ... ... ... He descended into Hell.
... ... ... The third day he rose again from the dead
... ... He ascended into heaven
... and is seated at the right hand of God the Father Almighty
from whence he shall come to judge both the living and the dead.
Isn't that cool? I've also heard Christ's descent into Hell described as a victory parade, referencing Ephesians 4 -
Eph 4:4 There is one body and one Spirit—just as you were called to the one hope that belongs to your call— 5 one Lord, one faith, one baptism, 6 one God and Father of all, who is over all and through all and in all. 7 But grace was given to each one of us according to the measure of Christ's gift. 8 Therefore it says,
“When he ascended on high he led a host of captives,
and he gave gifts to men.” [ref Ps 68:18]
9 (In saying, “He ascended,” what does it mean but that he had also descended into the lower regions, the earth? 10 He who descended is the one who also ascended far above all the heavens, that he might fill all things.)
Lutherans confess the descent into Hell as scriptural and creedal, but honestly we really don't spend a lot of time on it. The doctrine has moderate support in scripture, but not overwhelming support, and it is not an essential doctrine as far as justification is concerned.