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'.
(..) Okay, that way. That, no good. That, worse. Let's go. The river. How are we gonna get to the geyser? - Water's boiling. - We need something that floats. Anything. I could use a log or... What we really need is a boat. Who had dibs again? Come on, jump in. (..)2008 Journey to the Center of the Earth