An octopus has three hearts.

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Which seems excessive.

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Until you find out one of them apparently clocks out every time the octopus goes swimming.

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Two of its hearts are called branchial hearts.

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Their job is to pump blood through the gills, where it picks up oxygen.

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The third is the systemic heart.

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That one pumps oxygenated blood through the rest of the body.

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Three hearts.

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Everybody has a job.

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Then the octopus starts swimming.

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And the systemic heart stops beating.

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Not forever.

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Just while it's swimming.

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This is one reason swimming takes a lot of energy for an octopus.

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So, whenever possible, octopuses prefer crawling along the ocean floor using their arms rather than swimming.

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There's another weird part.

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Octopus blood is blue.

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Instead of using iron-rich hemoglobin to carry oxygen like we do, octopuses use hemocyanin, which contains copper.

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Apparently, when you have eight arms, blue blood and three hearts, having one of them take a break mid-swim doesn't even make the top  of the weird list.