Smeagol hilaris has only been collected from a small isolated location at Merry Beach, south of Ulladulla, New South Wales, Australia.
Smeagol hilaris is a pulmonate slug and is one of five species in the genus Smeagol. Pulmonate slugs have developed lungs instead of gills and can breathe air. Smeagol hilaris lives in gravel and cobble filled rocky crevices at Merry Beach. Little is known about their ecology or reproductive biology.