The Ryan siblings, Kevin and Holly Ryan, set out on a delightful kayaking trip near St. Augustine, Florida, enjoying the company of playful dolphins. However, their serene outing takes a dramatic turn when they cross paths with Winston Mills, a cunning businessman with ambitious plans for the local cove. Their leisurely adventure comes to an abrupt halt when a boat crash leaves them in peril; fortunately, a courageous dolphin comes to Holly's rescue, bringing her back from the brink of drowning.
Following their late return, their father, Bob Ryan, grounds both Kevin and Holly for not wearing life vests, but Holly can't shake the feeling that something is off with one of the dolphins. Their mother, Abby Ryan, takes her children out on their boat, where Holly discovers that one of the dolphins is missing, prompting her and Kevin to plaster the town with missing posters. Their search leads them to Marineland, where they uncover that the dolphin, named Bernie, has been rescued and is currently undergoing treatment.
Simultaneously, Winston Mills discusses his plans with Bob's superior, Luke Lawson, to construct an ocean park on Bob's land, sweetening the pot with the promise of a promotion for Bob. Unimpressed with this scheme, Kevin and Holly decide to concentrate their efforts on helping Bernie recover and reunite him with his pod. While filming Bernie's family in hopes of bringing them back together, they inadvertently overhear a sinister conversation between Winston and Mayor Brock Winters regarding an underhanded plan to steal turtle eggs.
In another scenario, Bob attempts to finalize the ocean park deal with Luke, but his children’s warnings about Winston's dubious intentions go unheeded. Their family celebration for Bob's promotion takes a dark turn when they find their filming location suspiciously deserted.
That night, Kevin devises a plan to recover his pilfered camera from Winston. Joined by Holly, they sneak into his office, where they overhear Winston disclosing that their father has unknowingly granted permission for an illegal chemical plant instead of the ocean park. Although Winston catches them red-handed, the siblings manage a narrow escape and encounter Sidney, a friend from Marineland. Winston pursues them furiously, leading to a chaotic moment where he breaks Sidney's phone.
As Sidney helps bring the children back to safety, Abby offers her technical expertise for repairing the shattered phone, while Bob remains skeptical about the children's claims. However, Abby and Sidney's convincing testimonies bring their story to light. The following day, Bob confronts Winston regarding the clandestine chemical plant, receiving a chilling threat in return: Winston will ensure Bob is imprisoned alongside him, thanks to Bob's own signature on the permits. Frustrated and overwhelmed, Bob decides to resign from his position.
Meanwhile, Abby successfully repairs Sidney's phone, and Kevin and Holly take it upon themselves to expose the nefarious plans of Winston. As they piece together the truth, including Winston's intention to acquire Marineland, Bob feels remorse for dismissing their concerns at first. He realizes, however, that their testimonies alone may not suffice for a conviction. Undaunted, Abby suggests they utilize Kevin's remarkable footage of marine mammals as critical evidence, leading Bob to contact a detective and secure police protection. Consequently, Winston and Mayor Winters face arrest.
In a separate, uplifting thread, Bernie fully recovers from his earlier sunburn and joins the Ryans on a mission to find his family in the ocean. Kevin and Holly share their adventure with the media, revealing their crucial role in unveiling Winston’s and the mayor's malicious plots. They outline their plans to return Bernie back to the wild where he can reunite with his kin. Ultimately, they manage to locate Bernie's family on a nearby beach, leading to a heartwarming reunion amid a gathering of intrigued onlookers.
