"Under that" can be replaced by several synonyms to diversify your language and add variety to your writing. Some of the synonyms for "under that" include below, beneath, covered by, hidden by, enclosed by, or surrounded by. Each of these synonyms has a similar meaning to "under that", indicating something that is located or situated beneath or covered by a particular object or surface. Using different synonyms effectively in your writing can make your sentences more engaging and build a stronger connection with your readers. Try experimenting with these synonyms to see how they can help enhance your writing style.