A bowl with a hole in its base will sink when placed in water. The Saxons used this device for timing purposes. Investigate the parameters that determine the time of sinking.
柴声都,刘丰硕,赵幼楠,陈伊颖,张瀚予
http://stemfellowship.org/iypt-2020-references-2/iypt-2020-reference-problem-6-saxon-bowl/