This activity demonstrates to students how water temperature and the concentration of dissolved and suspended solids affect the density of sea water. They will use various materials, such as salt and food coloring, to create and test water of different densities and record the time it takes drops of different water to sink through a mineral oil cylinder. In the second part of the activity, students will add the different colored waters to mineral oil and sketch what they observe, then describe what happens when liquids of different temperatures are mixed and when a clay and water mixture is poured into clear water. A student worksheet and discussion questions are included.