There are several reasons to float lanterns during the Loy Kratong festival, but the most common ones are:
1. To thank the Goddess of water Phra Mae Khongkha for letting us use water in our daily lives and to apologize to her for polluting it when showering and washing, etc.
2. To pay respect to the Buddha footprints on Nammatanati river bank in India.
3. To symbolically let go of unhappiness and sickness we put a coin, fingernail or a strand of hair in the lantern with the candle, incense sticks and the decorated flowers. Then, we let the lantern float away...
By showing respect to the Goddess of Water, we stop for a moment to think of the benefits we receive from it. At the same time, we can reflect whether we ever waste or pollute water and learn to use it more wisely.