The Indonesian Government argues that the sea bridges the many islands and different peoples of Indonesia. Politically, this might be appropriate as a means of encouraging people to think that wherever and whoever there are, they are united as Indonesians. However, when this ideology is used for maritime resource management, it creates problems. One issue derives from the fact that people do not think that the Indonesian sea is ‘free for all’ Indonesians. This paper argues that people, however vaguely, talk about ‘we’ and ‘they’ in defining who has the right to a particular fishing ground and who should be excluded. By analyzing conflicts that have taken part in different places in Indonesia, it demonstrates that ethnicity and regionalism have been used as the defining factor of ‘We’ and ‘They.’ In particular contexts, ethnicity and regionalism define whether fishermen can access marine resources. Thus, at the practical level the sea does not unite Indonesians, and it is in fact, ethnicity and regionalism that divides the Indonesian seas.