Composite materials, which have commonly been used in recreational boats, are now being applied to more challenging marine applications. The high specific stiffness and strength of composites translates into increased range and payload. Composites offer the added benefits of corrosion and erosion resistance, fatigue and wear resistance, reduced signature, and reduced maintenance and life cycle costs as compared to traditional metallic structures. Although ultrasonic techniques are typically used to inspect composite structures, thick composites, such as those used in marine applications, are difficult to inspect with ordinary ultrasonic methods. An ultrasonic inspection system is being developed for the US Army to inspect thick composite materials for future armored vehicles. This system is an extension of the existing PARIS flexible array ultrasonic inspection system, which was originally developed for inspecting thin composite aircraft structures. The extension is designed to increase ultrasonic penetration by 1) fabricating an array that operates at lower frequency and higher voltage, and 2) employing a synthetic pulse technique. The flexible array can rapidly inspect large areas and produce images of the inspection results that are easy to interpret. This paper describes the ultrasonic inspection system and presents examples of inspection results from both thick and thin composite materials.