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I guess nature landed on the periodic pump action as it is basically a muscle flexing.

Look at birds. Bird lungs aren't actually continuously-pumping, but are a relatively small step away from being so.

This?

TIL that birds are natures four stroke engines...

Don't some sea creature filter feeders have more or less continuous pumps?

IIRC some jellyfish do have continuous pumping mechanisms for propulsion, but I wouldn't put 100% faith on my memory right now