Water Clock
www.todayandtomorrow.net/2009/04/21/water-clock
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
To be able to read the Water Clock by Kyouei Design, you’ll have to let the white and red ball float in water. Inside the ceramic base are 2 magnets who rotate, those attract the 2 balls. The red one shows the hours, the white one the minutes.
found at designboom weblog