Due to high energy efficiency and fast data query, data-centric storage (DCS) is a promising technique for underwater acoustic sensor networks (UASN). However, the harsh sea environment poses new challenges to the design of underwater DCS protocols. First, because of long propagation delay and unreliably data links of underwater acoustic communications, long-distance multihop reliable data transport needs to be investigated. Secondly, due to the high node failure probability in the unattended UASNs, data reliability demands better protection. To address these two issues together, a fountain codes based reliable transport and storage (RTS) protocol is proposed in this paper. In the RTS protocol, a distributed fountain coding scheme is designed to facilitate reliable data delivery and multiple acknowledgements are adopted to ensure the control message reliability. In addition, to guarantee uniform data reliability, we devise a distributed storage scheme with concatenated fountain codes. Analyses are provided to reveal the performance of the proposed RTS protocol, which include storage reliability, energy consumption and number of retransmissions.