This study investigated the trends and correlations between ocean literacy (OL), marine science learning interest (MSLI), and marine science learning motivation (MSLM) in Taiwanese high school students in a three-wave longitudinal survey, with an OL scale used to assess students' MSLI and MSLM. A total of 428 valid responses were collected. The results indicated that the students' OL decreased by the second survey but slightly increased by the third. The MSLM scores exhibited an upward trend, whereas MSLI remained unchanged. A cross-lagged analysis revealed a consistently positive correlation between OL and MSLM across all three waves. Moreover, significant positive correlations between OL and MSLI and between earlier OL levels and later MSLI were observed, indicating OL plays a critical role in fostering MSLI. This study elucidates the associations between OL and MSLI and proposes directions for enhancing future OL education and research.