Please skip to 3:37 and take a look at how the s at the end of estamos(h) and entendais(h) are little bit different from the English s. It seems like in-between s and sh sound. I do not know if this is common in Spain or if this person is exaggerating. Is this the standard Castilian Spanish?
If anyone could also give me a link to a good website that clearly explains anything related specifically to this stuff, I'd be appreciated because I could not find much about this 'sh' in the Castilian Spanish.