Why a jellyfish is the ocean's most efficient swimmer

@article{Yong2013WhyAJ,
  title={Why a jellyfish is the ocean's most efficient swimmer},
  author={Ed Yong},
  journal={Nature},
  year={2013}
}
  • E. Yong
  • Published 7 October 2013
  • Environmental Science
  • Nature
Elastic body allows moon jellyfish to travel extra distance at no energy cost. 
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References

Passive energy recapture in jellyfish contributes to propulsive advantage over other metazoans
TLDR
It is demonstrated, contrary to prevailing views, that the jellyfish (Aurelia aurita) is one of the most energetically efficient propulsors on the planet, exhibiting a cost of transport lower than other metazoans and reduced metabolic demand by passive energy recapture improves the cost of travel by 48%, allowing jellyfish to achieve the large sizes required for sufficient prey encounters.