In many countries such as Thailand there is a tradition of letting lanterns float away into the sky during the autumn. These sky lanterns used to symbolize war, but, today, they symbolize good luck and new beginnings. The western world has adapted this practice to a way to send love letters. 

In Hawaii there is a similar phenomena in which the lanterns are placed in the water. These floating lanterns are released to honor the dead on memorial day and dedicate prayers for a peaceful and harmonious future. This ceremony is lead by her holiness, Keishu Shinso, in the Shinnyo-en Buddhist tradition. This tradition offers a system of training that is designed to help people reconnect with their natural warmth and kindness in a world with increasing complexities where people are becoming alienated from one other, a noble goal.

Finally, here is how to make your own floating lantern from Cultural China:

http://kaleidoscope.cultural-china.com/en/11Kaleidoscope7874.html

This could make for a great holiday celebration idea.