Today, the need for marine education has been declared for the conservation of marine life and the marine environment. Understanding the diversity of marine life is essential, especially since there are many organisms that live in the sea. The first step in understanding biodiversity is to follow your interest in exploring many different kinds of life. However, there are many opportunities for marine life education centered on fish, but few on decapodiform cephalopod education. Decapodiforms are morphologically diverse. However, the squid is generally recognized as a decapodiform, and little recognition of other types of decapodiforms is expected in marine education. To teach marine biodiversity more effectively, it is necessary to raise awareness of decapodiform diversity. In this study, we conducted a summer course for children using many specimens of different decapodiform species to understand decapodiform diversity. In addition, in order to examine students’ degree of recognition of decapodiform diversity, we asked students to draw decapodiform illustrations before and after the course. As expected, all participants drew a squid before the course. On the other hand, after the course, 58.3% of the students drew other decapodiform species. In the questionnaire survey about the course, more than 80% of students showed a high evaluation of impression and understanding. It seems that giving lectures on various types of decapodiforms is an effective way of raising awareness of decapodiform diversity.