This study explored public perceptions of the marine environment in three coastal communities in Greece and further investigated intentions to adopt behaviors that contribute to marine conservation. We used the Theory of Planned Behavior (TPB) to study the psychological determinants of behavioral intentions. The findings indicated that respondents have positive attitudes, moderate knowledge of marine issues, and they value the marine environment for the multiple ecosystem services that it provides. Litter and pollution from industry were considered as the most important marine threats, followed by fishing and farming. Participants suggested that informing the public and giving prominence to environmental education can contribute to marine conservation efforts. They felt that research centers and scientific community were more competent than governmental authorities and the private sector concerning the management and protection of the marine environment. Intention to adopt environmental behaviors was influenced by normative considerations, attitudes toward marine biodiversity and perceived behavioral control beliefs. The results may: 1) help inform policymakers to improve marine resource management towards a more sustainable relationship between people and the sea; 2) support the development of marine strategies that fit the social preferences, needs, and priorities to increase the likelihood of public support; and 3) support marine spatial planning efforts to uncover the intrinsic complexity of societal interactions with the marine environment. The findings further support policymakers that wish to promote behavior change through communication strategies that deliver environmental messages that focus on enhancing normative considerations, behavioral control beliefs, and corresponding attitudes.