Swordfish skeleton. (Photo: Postdlf/CC BY-SA 3.0)

Swordfish, not known for their beauty, also have oily faces, it turns out. But, according to a new study, their greasy skin may contribute to making the fish “reputedly the fastest swimmer on earth.”

The oil comes from a gland hidden under the base of a swordfish’s sword, New Scientist reports. One marine biologist found this gland in MRI scans of two swordfish, but for many years, it was unclear what the purpose of the gland might be. It took the discovery of a capillary network that connects the gland to the skin to make one possibility come clear—perhaps the oil contributes to swordfish speed.

The authors of the new paper, published in the Journal of Experimental Biology, hypothesize that the oil pours from the pores on the front of the swordfish’s head and lubricates its skin. Swordfish skin already has tiny, pointed denticles covering it, and combined with those features, that layer of oil, the researchers think, reduce friction between fish and water and help the fish swim more swiftly.

If only the oil that comes from human pores had an analogous effect.

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