The coastal defense structures are constructed by various types of structural systems varying from traditional rubble mound types and concrete systems to more innovative systems. In recent applications the geotextile is used in some applications of coastal engineering a such as coastal erosion control or perforated breakwaters. The tubular concrete units can be prepared at site by using geotextile as formwork and construct a perforated structure by placing the tubes in a specified angle and spacing. The performance of this type of perforated structures depends on the wave (height, period, direction) and structure characteristics (i.e. water depth, structure angle, bottom slope, tube spacing).. In this study, a perforated vertical wall structure constructed by placing the geotextile tubes with an angle of 45 degrees to the longitudinal axis of the breakwater is tested in hydraulic experiments. The experiments are conducted in a wave flume at a certain water depth and sea bottom slope under regular wave conditions with perpendicular wave approach. The transmission and reflection characteristics of wave heights are investigated. The relation between the reflection/transmission coefficients and the wave/structure characteristics are presented. The performance of this type of perforated structures is discussed.