An octopus has three hearts, and one of them stops when it swims.
Swimming exhausts it so fast that it would rather crawl across the seafloor.
Source
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More ocean facts
Ocean facts from a place we have mapped less thoroughly than Mars. A male anglerfish merges with his mate for good, there are lakes at the bottom of the ocean, and below about 8,400 metres there are no fish at all. Each fact links to its source.
- A male anglerfish merges with his mate. Permanently.
- Sensitive instruments are still built from steel salvaged off warships sunk before 1945.
- The Mediterranean dried to salt flats around five million years ago.
- There are lakes at the bottom of the ocean.
- The most abundant photosynthetic organism on Earth was not discovered until 1986.
- The Portuguese man o' war is not one animal.