pontoon vs snorkel

pontoon

noun
  • A float of a seaplane. 

  • A lighter or barge used for loading or unloading ships. 

  • A bridge with floating supports. 

  • A card game in which the object is to obtain cards whose value adds up to, or nearly to, 21 but not exceed it. 

  • A box used to raise a sunken vessel. 

  • A flat-bottomed boat or other floating structure used as a buoyant support for a temporary bridge, dock or landing stage. 

snorkel

noun
  • A retractable tube fitted in diesel-engine submarines to allow sufficient ventilation that the engines may be used at periscope depth. 

  • A snorkel parka. 

  • A hollow tube, held in the mouth, or mounted on and opening into a diving mask, used by swimmers for breathing underwater. 

verb
  • To use a snorkel. 

How often have the words pontoon and snorkel occurred in a corpus of books? (source: Google Ngram Viewer )