The first degree of diver insignia is SCUBA Diver. Dabas is also a trained scuba diver and underwater photographer. She is an avid scuba diver and painter. Leonov had trained as a scuba diver. She is also a certified scuba diver. Clarke was an avid scuba diver and a member of the Underwater Explorers Club. Cooper, who was a trained scuba diver, did most of his own underwater scenes. These standards include "Commercial SCUBA Diver". Neutral buoyancy in a diver is an unstable state. He is an experienced cave diver. Buoyancy and trim can significantly affect drag of a diver. The LUIS is another imaging sonar for use by a diver. Sebera started working as a diver and started gymnastics. Additionally, Fassbender modeled his walk around American Olympic diver Greg Louganis. This hinders research which could improve diver safety.