PolyPlus's battery may be just that: dip the encapsulated lithium pack into a glass of ordinary water and it produces current that lights up an LED display at the company's conference showcase booth.

By the light of each year's last full moon, Thais launch banana-leaf krathong floats-and their hopes for good fortune-in waters all over Thailand.

But when he held his flash light to the house, it was already completely under water.