Marine Officer Candidates quickly file onto a bus during an Officer Candidate School Preparation weekend at Camp Dodge, Des Moines, Iowa, April 24. The OCS Prep weekend is designed to give candidates a glimpse into what OCS life is like. - Marine Officer Candidates quickly file onto a bus during an Officer Candidate School Preparation weekend at Camp Dodge, Des Moines, Iowa, April 24. The OCS Prep weekend is designed to give candidates a glimpse into what OCS life is like.