Question

At what temperature is water most dense

Answer 1

Water is said to be the densest at $39°\mathrm{F}/4.0°\mathrm{C}$ ($3.98°\mathrm{C}$ to be exact). It is least dense at $0°\mathrm{C}$ (freezing point). The density of water greatly depends on the temperature and its salinity. It changes based on these two factors.