In case there's any confusion, the intro is the bit that Stoick whistles. The song starts off 
pretty slow and gradually picks up speed; by the key change it is quite fast. 

e|---------0---------0----3--------------0|---------0---------0----3-------------|
B|--------------3--------------3----1-----|--------------3--------------3-------1|
G|----2-----------------------------------|----2---------------------------------|
D|----------------------------------------|--------------------------------------|
A|----------------------------------------|--------------------------------------|
E|----------------------------------------|--------------------------------------|

e|---------0---------0----3--------------0|-----------------------0---------0----|
B|--------------3--------------3----1-----|--------3----1----3---------1---------|
G|----2-----------------------------------|---------------------------------2----|
D|----------------------------------------|--------------------------------------|
A|----------------------------------------|--------------------------------------|
E|----------------------------------------|--------------------------------------|

Stoick:
     Am               G      Am
I'll swim and sail on savage seas
                     G    C
With ne'er a fear of drowning
    Am              G        Am
And gladly ride the waves of life
   G              F Am
If you will marry me

   Am                 G        Am
No scorching sun, nor freezing cold
                   G   C
Will stop me on my journey
   Am               G       Am
If you will promise me your heart
    F            
And love-

Valka:
    F            G
And love me for eternity

   Am              G       Am
My dearest one, my darling dear
                     G    C
Your mighty words astound me
    Am              G      Am
But I've no need of mighty deeds
       G                F    Am
When I feel your arms around me

Stoick
    Am                G        Am
But I would bring you rings of gold
                  G  C
I'd even sing you poetry
    Am               G        Am
And I would keep you from all harm
   G                F    Am
If you would stay beside me

Valka:
  Am              G        Am
I have no use for rings of gold
                    G  C
I care not for your poetry
  Am             G       Am
I only want your hand to hold  
Stoick:
  G             F    Am
I only want you near me

Both:
   Bm               A         Bm
To love and kiss, to sweetly hold
        Bm             A   D
For the dancing and the dreaming
        Bm                A     Bm
Through all life's sorrows and delights
     A                 G   Bm
I'll keep your love inside me

     Bm              A      Bm
I'll swim and sail on savage seas
     Bm             A   D
With ne'er a fear of drowning
    Bm             A        Bm
And gladly ride the waves of life
   A        G     Bm
If you will marry me



This is an amazing song and I really hope it catches on. So do your part! Learn it! Play it! 
Put it on Youtube!