Scooby-Doo! Curse of the Lake Monster (2010) on Netflix

Plot summary

Summer break sends Shaggy, Scooby-Doo, Fred, Daphne and Velma to Erie Point, where Daphne's uncle Thornton Blake V has given them jobs at his country club so they can work off damages from an earlier mystery. A frog monster crashes the club's opening celebration, and a lake monster is sighted in the water. The lighthouse keeper Elmer Uggins, who alone has taken a picture of the creature, relates the tale of Wanda Grubwort, a witch who lived in Erie Point, warned the settlers away, and used a moonstone-powered staff to turn a frog into a monster. Velma finds security footage showing the lake monster meeting a cloaked figure on the beach, and the group tries to read the figure's face before the footage is ruined.