From WordNet (r) 2.0 (August 2003) [wn]:
snorkel
n 1: 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
2: air passage provided by a retractable device containing
intake and exhaust pipes; permits a submarine to stay
submerged for extended periods of time [syn: schnorkel,
schnorchel, snorkel breather, breather]
v : dive with a snorkel