The tabletop interface has been touted to merge the best of traditional board gaming and cutting edge computer technology in bringing both intense social interaction and limitless virtual representation to users. This study utilizes flow theory to understand user's enjoyment of playing games. It also explores the interplay between communicative behaviors and game play. Combining observations and questionnaire, data analysis showed certain nonverbal behaviors are correlated with flow. To further explain how social interaction influence game enjoyment, three main themes were identified: through the use of space, reduced nonverbal cues and knowledge transfer. Implications for tabletop game interface design are then discussed.