posted by SUSU .
I need to design an object that will sink when placed in a 20-gallon tank of room temperature water. After 30 seconds all or part of the object must resurface and remain floating. Closest to 30 seconds wins. I may not use Alka-Seltzer or any similar product! I may not touch the object once it's placed in the aquarium.
objects that allow bulbs to light when inserted in a circuit