Breathing Tube

Towards the end of the Second World War, some German U-boats were fitted with a retractable tubular vent that could be raised above the surface to take in air, enabling the craft to run on diesel engines while submerged, and at the same time recharge its electric motors.

The air-vent, or snorkel, enabled U-boats to remain operational yet relatively safe from the watchful eyes of Allied destroyers. Ingenious though it was, it was scarcely new, not by a million years or so. The water scorpion is one of several insects that make use of a similar device and for similar reasons - to be both operational and invisible. Its long tail, which gives it a passing resemblance to the land scorpion, is in fact a breathing tube that the creature thrusts above the surface of a pond edge or ditch while its front end clings to a weed stalk under water, wathing for prey.

An even more advanced adaptation has been made by rat-tailed maggots, the larvae of drone flies that live in ponds. The maggot can extend its tail upwards as much as 6 in (15 cm) to reach the surface. It is a true snorkel in that it supplies oxygen to gills in the maggot's rear end.