He could feel the anger 'boiling up' inside him. [=he could feel himself becoming very angry]
The water in the pot is 'boiling over'. = The pot (of water) is 'boiling over'.
The kettle (of water) is 'boiling'. = The water in the kettle is 'boiling'.
(..) At the Old Bailey we have Reichenbach hero Sherlock Holmes... Would you mind slipping your hand into my pocket? Thanks. # It was boiling, I ran to the sea # It was boiling I ran to the sea... # Crown v Moriarty, please proceed to Court . You're him. (..)2012 TvShow: Sherlock Title: The Reichenbach Fall Season: 2 Episode 3