Technically, demonstrative adjectives are typically used with countable nouns, referring to specific objects or people. However, there are some cases where you might use a demonstrative adjective with uncountable nouns like "water" or "sand" for emphasis or to express a particular context. It may not be the most common usage, but it can still be employed to convey a specific meaning. For example: "I love this water." Here, "this" with "water" implies a specific type or quality of water. It could be a particular brand, source, or even water temperature you are referring to. "Look at that sand." By using "that" with "sand," you might be pointing out a specific area of sand or emphasising its unique characteristics, such as its texture or colour. In these instances, the demonstrative adjective adds emphasis or specificity to the non-countable noun, highlighting a particular aspect or quality that you want to draw attention to.