The effect of a Water Candle is not improved or weakened by stacks, it will work as if there is only one.
No, candles do not float in water because they are denser than water and will sink.
Yes, just like on Harry Potter. In all seriousness, it depends on the density of the candle.
In Terraria on console, you can find the Water Bolt spell book in the Dungeon. To access the Dungeon, you need to defeat Skeletron, the guardian of the Dungeon, which requires you to defeat the Eye of Cthulhu first. Once inside, look for blue bookshelves, as the Water Bolt is located within those. Be cautious of the enemies that inhabit the Dungeon while you search for it.
Candles burn fuel (wax) in the presence of air and form carbon dioxide and water
I prefer scented candles over unscented candles. To me it is the wax that makes a difference. I really don't care for paraffin wax. I like palm wax candles. It burns cooler, cleaner, and has a better scent throw. I also prefer palm wax candles over paraffin wax candles because of the clean up. Unlike paraffin candles, palm wax candles can be cleaned with warm soap and water.
They are worse above water because it takes effect to people. Waves can wash the human race right out with one huge powerful hit.
Carbon dioxide (CO2) is the most powerful absorber of longwave radiation emitted by Earth, leading to the greenhouse effect and global warming.
The most powerful water type is Suicune.
The most powerful water type pokemons are kyogre and Palkia. Wrong. Palkia and Lugia tie for it. Kyogre is less powerful. But Arceus with the Water Plate could be considered more powerful.
the mass decreases as the wax burns so it displaces less water
Yes, many pool supply companies sell candles holders that float in water. You can keep the holder for years and replace the small candle inside.
Any oil that escapes the burning and goes to the surface of the water will seal the water membrane and prevent fresh oxygen from dissolving in the water. The heat will warm the water, which isn't good for the fish and also lowers the oxygen content. Fish are living things, not toys and candles in the water is a bad choice and cannot be good for them.