Deep wading or deep fording is a technique used by some heavy semi-amphibious vehicles to traverse water that is several meters deep – the vehicle drives on the riverbed/lakebed/seabed and uses screens or a pipe (a snorkel) that reaches above the water surface for an air supply. The technique has been used by armored military vehicles such as tanks and armored personnel carriers. Deep fording generally implies driving through water of such a depth that the vehicle is mostly or entirely submerged by the water, sometimes to several times the height of the vehicle itself, as well as a sealed crew compartment, complete with air supply for the crew. This makes it different from the less extreme “wading” done by many off-road vehicles which are simply fitted with a snorkel that is higher than the normal engine air intake, roughly level with the top of the cab. In these cases, the crew compartment is not watertight, and the snorkel provides air only for the engine. Thus maximum height is limited by the crew’s need to breathe, and very rarely completely submerges the vehicle.

In contrast, lighter, true-amphibious vehicles that float on the water surface are not limited by the depth of the water.

Although Duplex Drive allowed landing craft to release tanks farther from shore, the alternative deep wading gear permitted a tank to drive partially or completely underwater on the sea floor rather than swim. Deep wading Churchills took part in the 1942 Dieppe raid, and also operated during the D-Day assault. These tanks were given waterproofed hulls and air intake and exhaust trunking to allow them to come ashore from shallow water. Tall ducts extended from the engine deck to above the turret top and they needed to stay above water. The front duct was the air intake for the engine and crew compartment, the rear duct vented the exhaust. This device saw use in many amphibious operations, it was also used on light tanks and tank destroyers. The US had similar devices for trucks and jeeps.

The Germans gave their Tiger tank a long snorkel, essentially a long tube on the commander’s hatch that allowed it to wade through up to four metres of water, as well as rubber gaskets on all openings. This was necessary because the large tank was too heavy for most bridges in Europe and Russia at the time, meaning that they had to be able to deep ford across rivers when a bridge was not available. The Tiger was the first tank to come with deep fording ability as designed, although the earlier Tauchpanzer, a modification of the Panzer III and Panzer IV, was designed to drive on the sea-bed, part of the German preparations for Operation Sea Lion, the planned invasion of Britain in 1941. A long, flexible rubber hose with a floating buoy on the end supplied the engine and crew with air and gave the waterproofed tank a maximum diving depth of 15 metres (49 ft) making it an extreme example of a wading tank. They were also extremely unpopular with their crew, because they were in danger of breaking down in deep water and drowning the crew. Since the crew was unable to see where they were going, direction was given by means of radio and a spotter on the surface. The Germans eventually converted 168 Panzer IIIs and 42 Panzer IVs into Tauchpanzers, although they were never used for their intended purpose in the end.

The Pacific Theatre of Operations had its own set of unique obstacles and consequential techniques aimed at overcoming the challenges posed by forcible entry by sea. Though the Marine Corps was accustomed to landing individual tanks using LCM (Landing Craft Mechanized), it profited from massive landing operations to combat test an alternative innovation: the pontoon-based T6 flotation device which allowed a Sherman’s main gun to be used as it swam to shore.

As detailed in Oscar Gilbert’s Marine Tank Battles in the Pacific, two platoons in each battalion combat-tested the bulky system, which proved more seaworthy than the ill-fated Sherman Duplex Drive amphibious tanks at Normandy, but not necessarily more useful as it took the Shermans five hours to swim ten miles to shore.

“The lead tank of the 1st Tank Battalion detachment, commanded by Sergeant D.I. Bahde, immediately ran afoul of a passing destroyer. Unable to speed up, slow down, or steer adequately, the tank plowed inexorably toward the ship, which refused to give way. The tank crashed into the side of the ship, achieving the dubious honor of being the only tank ever to ram a ship at sea.“

But it wasn’t long before Marine tankers were soon heavily engaged with the nearly 100,000 Japanese soldiers and conscripted civilians defending the island.

By then the Marine tankers had perfected a “corkscrew and blow torch” in which they plastered a sector of the battlefield with main gunfire, before tanks with hull-mounted auxiliary flamethrowers rooted out the survivors.

Riflemen covered tanks from behind to ward of suicide assaults and the tankers even called down air-bursting artillery to spray shrapnel over their own turrets for added protection. Some Marine Shermans sported arrays of M2A1 anti-personnel mines on their hulls which could be remotely detonated as a last-ditch defensive measure.

Thanks to these tactics and the open terrain, Marine tank losses to close assaults were reduced to nil, contrary to the fortunes of less-experienced Army tank units.

Look for Forces of Valor’s latest M4 Sherman tank, equipped with both deep wading gear and a flamethrower, to storm ashore later this year.