The phrase "skin deep" means that something or someone appears to be attractive or good on the surface but lacks substance or depth beneath. There are several synonyms for this phrase that convey the same idea, such as superficial, shallow, veneer, façade, appearance, and outwardly attractive. All of these words highlight the idea of something or someone being only surface-level and lacking any true meaning or value underneath. Therefore, it is important to look beyond shallow appearances to truly understand the essence of someone or something. These synonyms serve as a reminder that true beauty and worth reside within, not just on the surface.