In 1970s Maine, bankrupt fisherman Cliff rescues Ivy, a four-year-old mermaid. With her magic and radar, Ivy helps him find tuna and pink diamonds. When tycoon Vance sabotages the harbor, Ivy guides the family through underground rivers to Boston. Cliff defeats Vance, buys the mansion and dock, adopts Ivy, and finds wealth, love, and redemption.
