http://youtu.be/wJr4NcxNfdQ

ok. so far I've been contemplating and listening to both versions (Switchfoot and Mandy Moore) and so I chose the piano version from the movie: a walk to remember ('cos there's more to analyse i hope)

the chords go smthg like that so far. till the bridge.
C#-(Verse):
A E A46-57 G#m7
C#m E64 A E A G#m7 x3
C#m E64 A E A G#7 (enharmonic reinterpretation of the C# note to Bx)

Transposition to C#+(Chorus: relative major):
C#8-7 F#
C#8-7 (F# A#247-35-247-35) x2 A57-46

C#-(transition to verse):
C#m7 C#m65 A G#M7-m7 (now the B# becomes the leading note which resolves towards the C#)

Bridge (the tricky bit)
B C#42-31 B C#42 the next chord sounds like a G#65 'cos of the lower B# neighbour while the 42 in C# is suspended which then resolves to C#31

D# D#42 G#65 (F#6) G# (now effectively tonicized to G# by V - V42 - I6 - vii dim6 - I. with the bass going D# C# B# A# G#)

(In case you're as lost as I was, we're now at the part of ~at the top of my lungs~)
F#(vii dim?) G# F# (E# vi?) D# G#
now the question is why isn't it Fx and F# instead? did he/she modulate to the G Ionian instead? interesting!

then it goes back to the verse with a nice perfect cadence G# to C#.