Claire in Hailey sta navihani najstnici in najboljši prijateljici. Skupaj preživljata še zadnje dneve, saj se bo Hailey potem z mamo preselila v Avstralijo. In kakšna avantura ju čaka! Nekega dne v bazenu odkrijeta čisto pravo morsko deklico Aquamarine. Lepa svetlolaska je pobegnila od doma, da bi se izognila dogovorjeni poroki in našla pravo ljubezen. Le tri dni časa ima, da svojega očeta prepriča, da ljubezen ni mit. Claire in Hailey ji seveda priskočita na pomoč, ko se Aquamarine odloči osvojiti čednega reševalca Raymonda.
In a dreary Florida beach resort village, luscious-limbed lifeguard Raymond is the main attraction for girls. Teenager buddies Claire and Hailey became experts on him by observation, but never dared actually approach him, and after this closing summer season will be separated as one's parents move to Australia. Then they find a storm washed up in a pool a sassy mermaid, who promises them a wish if they help her prove to Neptune love exists, and Raymond is the only creature resembling a love-god.