BELFAST, Maine — This summer, the city of Belfast is under invasion by a group of fantastic sea creatures that are unlike anything found in the oceans.

The 21 sea creatures belong to the new Waldo County Children’s Mural Project, which is highlighting original art from elementary school children from around the county. There is a blue, grinning fish, a striped cross between a unicorn and a mermaid, a psychedelic jellyfish and many more whimsical and weird creations. And they are being painted onto an existing mural, the S.S. Belfast, which enlivens the concrete wall of the Family Dollar Store on Main Street.

“They are cool,” Belfast artist David Hurley, who had the idea for the children’s mural project, said Friday. “There are amazing colors and designs. … Public art belongs to all of us. It’s part of who we are. Especially living in a culture that’s so commercial and materialistic. I think public art is a way of saying we’re more than that.”

Hurley said that the project actually began years ago, when he and artist Russell Kahn painted the S.S. Belfast on the wall, which is about 100 feet long and 20 feet high. It’s a big space, and the ship did not fill it all up.

“It always included a second phase — of children painting fantastic sea creatures,” he said.

So last year, Hurley and Kahn sought and won a $4,000 grant from the Maine Community Foundation to bring the vision into reality. They held a contest, open to every elementary school-aged child in Waldo County, seeking their ideas of a sea creature.

“I said they can be creatures that exist now, or in the past. They can be creatures that exist in your imagination,” Hurley said. “They can be funny. You can tell me where they live and where they eat. Kids don’t have to learn to be creative. They are creative.”

And so the art began pouring in. The two muralists received 198 submissions altogether, and began the hard work of narrowing them down to 21. Hurley and Kahn got local businesses to sponsor the creatures, and in late May, a group of adult artists and the young artists who won the competition began pairing up to paint the art on the walls of the building.

The work will continue into July when it will be completed.

When it’s finished, Hurley said, all the artists involved will be given credit for their work with their names printed on the bottom of the mural and on a display case that will explain the mural to passers-by.

“All the names of the kid artists and the adult artists, so people can see it really was kind of a big community effort,” he said. “I hope that maybe these designs will remind people that art is a part of who we are. That it’s really fundamental to being a full person.”