Submarines played a crucial role in WWII, sinking vast numbers of merchant ships and threatening supply lines. Large-scale patrols were mounted with both ships and aircraft to hunt them down visually, as submarines had to spend much of their time on the surface. However, as a 1943 report from the Australian Navy’s Anti Submarine Warfare Division notes, it was easy to confuse submarines with whales.
The report was unearthed recently by a Twitter user who was struck by “possibly the cutest diagram in security studies.”
A section of the report, which is classified as ‘Secret,’ notes that fin and humpback whales tend to concentrate in specific areas of the South Pacific between June and October, and this had led to an increase in the number of errors. The report helpfully provides pictures to illustrate what whales look like and notes:
“Since they are warm-blooded mammals and breath air, whales cannot leave the surface for long periods. They break surface to breathe, expelling air and so causing the characteristic “spout” or “blow”. During this period the back is usually exposed, and it is then that the resemblance between whale and U-boat is greatest.”
While mistaking a whale for a U-boat could be fatal for the whale, there was a bigger problem from the Navy’s perspective of mistaking a submarine for a whale and letting it get away. While a submarine produces significant turbulence, the motion of a whale is much smoother: “A whale produces very little foam except when travelling at speed although the tail flukes often leave a series of swirls at the surface.”
The other tell-tale sign of a submarine was a slick of oil, which was often easily visible from the air. And while whales are famously known for containing large amounts of oil, the report notes that they do not spill it: “Most of the oil in a whale is contained in the blubber and bones … In no circumstances does any living whale exude oil or leave a film of oil on the water.”
This was not the first time that the confusion between whales and U-boats has been noted. In 1919, the Illustrated London News showed pictures taken during WWI, one captioned: “A Whale swimming under water photographed from the air: showing the resemblance to a submarine which caused many to be bombed.” The accompanying article explained that mistakes were easy to make in poor light, and that the rules was “When in doubt, bomb.”
Some U.S. Navy aviators made similar mistake in WWII. Patrol Squadron 53 (VP-53), which operated PBY-5 Catalina Flying Boats on long-range anti-submarine patrols even invented a spoof “Royal Order of Whale Bangers.” This was a medal ceremonially awarded to any bombardier who accidentally bombed a whale instead of a submarine.
Modern anti-submarine warfare is carried out largely using sonar, and whales and submarines are unlikely to be confused. However, passive sonar – which detects the sound made by an object rather than reflecting pings off it – may have trouble with unusual noises. In the 1990s, the Swedish Navy believed that they had repeatedly detected the sound of Russian submarines intruding into their waters. However, when they shared their classified recordings with two university scientists, it turned out the sounds were actually made by panicking shoals of herring. Magnus Wahlberg and Håkan Westerberg won an Ig Nobel Prize for this discovery.
It is also believed that during the 1982 Falklands conflict, the British type 22 frigate HMS Brilliant fired torpedoes at sonar contacts which turned out to be whales. This was only revealed by crew diaries in 2013.
Modern sonar is far more discriminating, and unlikely to make this type of mistake –at least with conventional underwater craft. In recent years researchers have been turning to biomimetic designs which seek to take advantage of the efficient hydrodynamics of sea creatures. The Ghost Swimmer developed by Boston Engineering for the U.S. Navy is one such design. It propels itself with a powerful tailfin like a dolphin or shark, to achieve both stealth and high maneuverability. Ghost Swimmer looks more like a living thing than a robot.
The full-size SMX31E concept submarine from European designers Naval Group has conventional propulsion but the overall design is borrowed directly from a whale. This suggests that future submarines may become increasingly more animal-like. “U-Boat or Whale?” may again become more of a challenge.