According to Wikipedia, the swordfish is named after its bill resembling a sword. This makes it superficially similar to other billfish such as marlin, but upon examination their physiology is quite different and they are members of different families.
original watercolor sketch
After I battled one of these for nearly a day before bringing him close enough to the boat to permit a quick touch before the deckhand returned him to the ocean, I hardly knew whether he was a marlin or a swordfish. But I did notice he was huge and heavy.
Have you challenged an Xiphias?
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