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> They are shown to have a biological clock, even thought they are balls of single cells:
> 
> https://phys.org/news/2018-08-mystery-algae-balls.html
> 
> "Scientists from the University of Bristol have uncovered the age-old mystery of why marimo algae balls sink at night and float during the day. 
> 
> "The balls are a rare form of algae found naturally in lakes in the northern hemisphere, particularly Japan and Iceland.
> 
> "In Japan they have such important cultural significance, they are a protected species. They are also very popular with aquarium owners, although, in recent years, their popularity has resulted in a significant decline.
> 
> "In a new paper, published today in the journal Current Biology, Bristol biologists have shown that photosynthesis and daily circadian rhythms are responsible for the floating and sinking of the balls.
> 
> "When these aquatic plants photosynthesise, they become covered in tiny bubbles of oxygen, which the scientists predicted was the cause of their buoyancy.
> 
> "They tested their theory by using a chemical that stops photosynthesis. The chemical stopped bubbles forming, so the marimo did not float.
> 
> "The lab then investigated whether the photosynthesising surface of the algae balls had a biological "clock" or circadian rhythm.
> 
> "Marimo were kept under dim red light for several days. They discovered that if the marimo were then given bright light at the time that corresponded to the start of the day, they floated much more rapidly than if they were given light at the middle of the day.
> 
> "This shows that marimo floating is controlled by their biological clock."
> 
> Comment:  Our 24-hour day has been encoded into most living organisms. The sinking or floating is not magical, just turning phosynthesis on or off.