With the outbreak of peer-to-peer applications and its great potential of file sharing, along with the rapid development of the marine telecommunication technologies, we feel the impulse to implement a mobile peer-to-peer file sharing system for the sea area, where the crew or passengers are far away from the land, expecting more for file and information sharing than people on shore. To achieve such a goal, we propose a mobile P2P architecture based on Next Generation Maritime Communication Network (NGMCN), which is kind of Heterogeneous Wireless Network (HWISE). In this paper, we design our mobile P2P overlay system, eSeagull, based on the proposed architecture. Through statistical analysis and simulation, it is demonstrated that this system is applicable and suitable for the marine domain.