air passage provided by a retractable device containing intake and exhaust pipes; permits a submarine to stay submerged for extended periods of time
breathing device consisting of a bent tube fitting into a swimmer's mouth and extending above the surface; allows swimmer to breathe while face down in the water
disposed to venture or take risks; "audacious visions of the total conquest of space"; "an audacious interpretation of two Jacobean dramas"; "the most daring of contemporary fiction writers"; "a venturesome investor"; "a venturous spirit"
unrestrained by convention or propriety; "an audacious trick to pull"; "a barefaced hypocrite"; "the most bodacious display of tourism this side of Anaheim"- Los Angeles Times; "bald-faced lies"; "brazen arrogance"; "the modern world with its quick material successes and insolent belief in the boundless possibilities of progress"- Bertrand Russell
invulnerable to fear or intimidation; "audacious explorers"; "fearless reporters and photographers"; "intrepid pioneers"