Two teenage girls discover that mermaids really do exist after a violent storm washes one ashore. The mermaid, a sassy creature named Aquamarine, is determined to prove to her father that real love exists, and enlists the girls' help in winning the heart of a handsome lifeguard.
| Actor | Role |
|---|---|
 Emma RobertsClaire Brown | Claire Brown |
 JoJoHailey Rogers | Hailey Rogers |
 Sara PaxtonAquamarine | Aquamarine |
 Jake McDormanRaymond | Raymond |
 Arielle KebbelCecilia Banks | Cecilia Banks |
 Claudia KarvanGinny Rogers | Ginny Rogers |
 Bruce SpenceLeonard | Leonard |
 Tammin SursokMarjorie | Marjorie |
 Roy BillingGrandpa Bob | Grandpa Bob |
 Julia BlakeGrandma Maggie | Grandma Maggie |
 Shaun MicallefStorm Banks | Storm Banks |
 Lulu McClatchyBonnie | Bonnie |
| NNatasha LeighPatty | Patty |
 Dichen LachmanBeth-Ann | Beth-Ann |
 Lincoln LewisTheo | Theo |
 Matthew OkineNick | Nick |
| RRegis BroadwayVince | Vince |
| RRobbie ParkinPool Guy | Pool Guy |
| JJoey MasseyLittle Boy | Little Boy |
| DDillon StephensenWaiter | Waiter |
| DDonna FoxFirewoman | Firewoman |
 Alice HunterBeach Girl | Beach Girl |
| AAdam KingShopkeeper | Shopkeeper |
 E. G. DailyWoman (uncredited) | Woman (uncredited) |
 Ozzie DevrishCarnie (uncredited) | Carnie (uncredited) |