These lights will last between 36 and 48 hours. You can put them in water and they will still work but the dye from the casing will start to leak. This will not ruin the glass vase.
These are powered by non replaceable batteries. Attached to each Floralyte II is an elastic string that can be used for hanging the light, or it can be removed. It is also attached to a black cord which can be used to suspend it into tall vases or floral designs. These are fantastic in small place-setting displays as well. They are ideal lighting for catering design.