Mermaids (2003)

Diana, a stubborn mermaid, is determined to bring justice to the men who killed her merman father. Never having lived out of water before, she enlists the help of her two sisters (already living on land) to track down the murderers. Diana finds that her sister, Venus, is an aquatic dancer in a seedy bar who was forced into the position by the evil bar owner who has taken Venus' magic tiara, giving him ultimate control of her. June, the third sister, works at the local aquarium and is able to recruit the help of her friend, and love interest, Randy, a coast guard officer, to help the mermaids track down their father's killers. The sisters join forces and along the way, discover how difficult it is to be a fish out of water, and how meaningful sisterhood is.