Everyone Loves Mel (1998)

Set in the beauty of the Pacific Northwest, the legend of Swanson Lake is kept by one man and he's not about to surrender it. When Bill's grandsons come for a summer visit, they stumble into a big-time adventure with a giant turtle named Mel. When Bill's neighbor Bailey tries to kidnap Mel in order to feature him in a proposed theme park, the grandsons plot to hide Mel from the neighbor.