Sand does not dissolve in water. Sand is mostly made of fine quartz, which does not dissolve in water. Sand does dissolve in certain hot acids.
A substance, known as a solute, dissolves in a solvent when the solvent is able to surround the solvent molecules and the solute becomes invisible to the naked eye. The non-polar covalent bonds in sand are too strong for water to break and surround the sand molecules. Like solvents dissolve like solutes; therefore, polar solvents, like water, dissolve polar solutes like salt and sugar but do not dissolve non-polar solutes, like oil. By contrast, a non-polar solvent dissolves a non-polar solute; thus salt does not dissolve in alcohol because alcohol is non-polar.