physics
posted by SUSU .
I need to design an object that will sink when placed in a 20gallon 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 AlkaSeltzer 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
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