<p>The hydrophobic modification method, which is commonly used to improve the corrosion resistance of cement-based materials, is reported to have drawbacks, including increased porosity and larger pore diameters in concrete. In this paper, a new method using coral sand as an internal curing material was proposed to optimize the pore structure of hydrophobic modified mortar. The interfacial transition zone of the mortar was analyzed to assess the varying impacts of coral sand and river sand on the pore structure within hydrophobically modified cement mortar. Due to the low surface energy of the modifier, a superhydrophobic coral sand mortar with a water contact angle of 152.2° was successfully prepared. Nuclear magnetic resonance technology was used to observe pore distribution of samples at different curing ages. This facilitated the clarification of how coral sand influences the pore structure across different wetting conditions. The proposed method is expected to refine the pore structure of superhydrophobic mortar, further improve corrosion resistance, and guide the use of durable superhydrophobic concrete in the future.</p>