ZacisateenageboywhodecidestocamponMakoIsland,unawarethatthreemermaids,Sirena,NixieandLyla,whoareguardiansoftheisland,arewatchinghim.Thatnight,whenthefullmoonrises,theboycomesintocontactwiththemagicwateroftheMoonPool.Thefollowingmorning,Zacwakesupdiscoveringhehasbecomeamermanwithafish-liketailandtheabilitytocontrolandmanipulatewater.Hisnew-foundmermanabilitieswillcauseproblemsforthemermaids.Thethreemermaids,curiousaboutlivingonland,aretransformedintohumanswhileinthemoonpoolduringafullmoon,nowhavingtheabilitytolivelikehumanccc
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