Question: What does the snorkel typically look like?
About the article "Snorkeling", section "Flooding and clearing".

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The Yochelcionellids have given rise to the "snorkel hypothesis".
These fossils are aseptate helcionellids with a snorkel-like tube on one surface.
The snorkel has been seized upon as characteristic of a cephalopod-like water circulatory system, or perhaps as a precursor to the siphuncle.
However, neither of these theories have been borne out. 
This genus of molluscs possessed shells which were shaped like curved caps, with an exhaust pipe shaped "snorkel" emanating underneath where the apex (point of the shell) curves over.
All experts agree that the "snorkel" was used in breathing, with most experts suspecting that it allowed waste water to flow away from the gills. 
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A vehicle snorkel is the land-based equivalent of the submarine snorkel which allowed submarines to use diesel engines while submerged.
Snorkels, when used by vehicles with air-breathing internal combustion engines, allow limited deep fording capability for river crossing or amphibious landing operations.
Military wheeled vehicles, like Jeeps, are capable of mounting snorkels for the air intake and engine exhaust, to allow them to wade through relatively deep water, limited by the height of the driver's head.
In the case of a Jeep, all of the engine openings and wiring are sealed, and the driver must first operate a damper that over-pressures the engine vacuum, to prevent water from entering.
After fording, the vehicle's wheel bearings must be repacked with new lubricants.
Tracked military vehicles such as tanks and armored personnel carriers generally operate with all hatches sealed and the crew fully enclosed by the vehicle.
Such snorkelling equipment is available as an aftermarket accessory for some civilian four-wheel drive vehicles.
The snorkel is typically routed out through one of the front wings and up beside the "A" pillar to the level of the roofline where it is terminated with either a mushroom intake or a forward-facing intake. 
The SCUBA equipment listed under the T/E set by the US Navy for the Marine Corps reconnaissance: Draeger LAR V rebreather unit — The rebreather unit is a SCUBA system that scrubs exhaled carbon dioxide and recycles it into breathable nitrogen/oxygen mixed gas.
Since it is closed-circuit, a trail of air bubbles does not reach the water's surface, which would reveal the location of the diver and compromise the mission.
Deep See Squeeze Lock – diving knife with a beta-titanium blade.
Useful when snagged in fishing nests or other submerged entanglements alike, when swimming underwater are almost non-visible.
Aqua Lung Military Snorkel Flex Tube — Standard-issue snorkel.
Aqua Lung Rocket Fin — Standard-issue swimfins.
Aqua Lung Look Mask and Mythos Mask — Standard-issue diving mask.
Mythos mask contains a blow-out, one-way valve at the nasal piece to expel water that is in the goggles.
Diver's Weight Belt, (WB67/WB68) – Weight belt is used to level buoyancy under the water.
Case Soft Diving Weights, (September-M-2/Sep-M-5) – Additional weights that can be released individually to proper buoyant level.
Scubapro Twin Jet Fins — Split fins are fairly new to the Marine Corps T/E, since 2000.
They have been tested to prove that the split fin design allows slightly better maneuverability if one had to immediately run during unexpected enemy contact once ashore.
It also has excellent water propulsion to push the recon Marines and Corpsmen to shore.
Aqua Lung Impulse 2 Snorkel — This snorkel contains a one-way valve that prevents water from entering the diver's mouth.
UDT life preserver — Standard-issued life preserver.