In my opinion, I think that the band is talking about a couple who think that they're deeply in love and think they are meant for each other, and dream of having the perfect life; A nice house, good jobs, raising a family, etc.
Soon after, they realize that all of this isn't easy to have. They realized they've been 'breathing underwater' because they've been fantasizing about a life that isn't meant to be, and they have to face reality.
In my opinion, I think that the band is talking about a couple who think that they're deeply in love and think they are meant for each other, and dream of having the perfect life; A nice house, good jobs, raising a family, etc.
Soon after, they realize that all of this isn't easy to have. They realized they've been 'breathing underwater' because they've been fantasizing about a life that isn't meant to be, and they have to face reality.
This song is amazing though <3