Happy Little Submarines: Adventure Island, the latest installment in a 15-year-old animated franchise, was released on Saturday, bringing joy in celebration of International Children's Day.

Families enjoyed an immersive theater experience at the film's premiere in Shougang Park in western Beijing on May 30. They participated in games inspired by the film and watched a chorus performance by a group of kindergarteners.

The four familiar anthropomorphic submarines reunite, and the new film follows their latest adventure as they battle a sea monster that creates an unprecedented crisis caused by a greedy one-eyed shark.

In addition to its fantastical and action-packed elements, the film infuses knowledge about prehistoric marine creatures and themes of ocean environmental protection into its plot twists to merge entertainment with educational value, according to the producers.

Over the past years, Happy Little Submarines has released 10 feature-length films and two seasons of an animated series, with a combined box-office gross revenue of 350 million yuan ($48.6 million).