The construction of tropical islands and reefs is challenged by the shortage of conventional building materials and the poor ductility of structures. These difficulties can be effectively addressed by utilizing seawater and coral sand to produce seawater coral sand engineered cementitious composites (SCECC). The stress-strain curves of SCECC under graded loading were analyzed, and the influences of polyvinyl alcohol (PVA) fiber content and curing age on its compressive strength, peak strain and compressive toughness were investigated. It was indicated from the results that when the PVA fiber volume fraction was up to 2.3%, the compressive strength of SCECC was improved with the increase in fiber content and curing age, and a 28-day compressive strength of 43.66 MPa was achieved, with obvious early-age strength development being observed. Additionally, the enhanced deformation resistance of SCECC was demonstrated by the incorporation of PVA fibers. An upward trend in both the peak strain and compressive toughness was generally exhibited with the increase in fiber content. Based on uniaxial graded loading tests on SCECC, the Maxwell viscoelastic constitutive model was introduced, and the functional relationships between the elastic modulus, viscosity coefficient and fiber content could be analyzed. At a fiber volume fraction of 2.300%, the elastic modulus of SCECC under graded loading was measured as 12.33 GPa, and the viscosity coefficient was determined as 4.56×10⁴ GPa·s.