In this paper, we introduce the studies and design for underwater acoustic digital data transmission system. Most of the hardware and the software of the system are designed and constituted by the project researchers. However using ASK (Amplitude Shift Keying) is not suitable for such a channel with noise and multipath effect, this modulation scheme is chosen for the hardware and software esae. In order to robust data transmission system for bit errors caused by syncronization problem in long data sizes, we split the data into frames. Each data imported into the system from the user interface is splited into frames which contains pre-information packet about the data and the data itself.