The word "more waterless" means having even less water than before. The antonyms for this could be phrases like "less arid," "more moist," or "more aqueous." If you're talking about a landscape or environment, some other antonyms could be "flooded," "saturated," or "waterlogged." In terms of personal thirst or hydration, antonyms for "more waterless" might include phrases like "well-hydrated," "quenched," or "satisfied." Whatever the context, there are plenty of opposite words and phrases that can express the idea of having more water or being less dry.