The underwater 'kites' generating electricity as they move

 https://www.bbc.com/news/business-59401199

"two kites - with a five-metre (16ft) wingspan - move underwater in a figure-of-eight pattern, absorbing energy from the running tide. They are tethered to the fjord seabed by 40-metre metal cables... moving "flight path" allows the kite to sweep a larger area at a speed several times greater than that of the underwater current... on-board computer steers the kite into the prevailing current, then idles it at slack tide... Each kite can produce enough electricity to power approximately 50 to 70 homes"

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