Sometimes the marvelous things around us seem so familiar that they become almost humdrum, but it’s only when we truly look at them in detail that they become wondrous again.

Take swordfish for example. With their distinctive shape and near-legendary swimming speed, they’re certainly unusual at first glance, but despite that fact that we’ve known about them, fished them and eaten them for hundreds of years, it turns out that we still don’t know everything about their bodies and they are still capable of serving up some amazing surprises.

 Such was the discovery made by scientists in the Netherlands. While examining the structure of a swordfish’s bill using an MRI scanner, they discovered that it was as rough as sandpaper and covered with tiny holes near its tip. Further study showed that, much like the pitted surface of a golf ball, the texture and holes were perfect for reducing the fish’s drag through the water by preventing turbulence and thus helping it swim even faster.

The scientists also discovered a mysterious and previously unknown fist-sized oily gland above the base of the bill and between the animal’s eyes. No-one had a clue what it was for and at first it was thought that it had something to do with the fish’s olfactory system. The mystery remained unsolved for eleven more years, but like some of the greatest scientific discoveries, the truth was revealed by accident. When a researcher was dropped a lightbulb on the fish’s head whilst taking photographs, it revealed a web of tiny blood vessels inside the skin that were connected to the mysterious gland. The vessels then open out into the fish’s skin via tiny pores, each just a fraction of a millimeter wide. After a bit of thought and a bit of time spent heating the gland with a hair-dryer, the congealed oil in the gland became liquid under the heat and oozed out of the fish’s pores.

The truth thus became clear and the gland was revealed as yet another drag-reducing adaptation, as its oil repels water and lets it flow smoothly over the surface of the bill. That depends on the oil staying warm, but swordfish have amazingly modified some of their eye muscles into heat-producing organs that their blood warm and sharpen their vision as they hunt. This same heating effect keeps the drag-reducing oil liquid and allows it to ooze out of the glands and help the fish reach the kinds of speeds that make it a true aquatic marvel.