I don't know a whole lot about waterbirth as I haven't yet had one, but I have provided some links to great pages on it, so do check them out if you are considering this. I highly recommend it as I loved labouring in the water. Sterilised Scissors if you plan on cutting the cord, if you are planning a lotus birth then this will be unnecessary. I have provided links for this as well, as again, this is not an area of expertise for me. Preferably peaceful music.
Candles are great and provide a terrific atmosphere.
Herbs such as Nettle , Alfalfa leaf infusion, Motherwort and Shepherd's Purse are terrific helps for preventing hemorrhage. Chux Pads are also a must. I plan on doing this from now on. Do not use dental floss , as those who have used it found that it cut right through the cord, and you do not want that. Some birth supply places sell clamps as well.