Marines conduct a gear rescue evolution during a Marine Corps Instructor of Water Survival course at the base pool on Marine Corps Base Hawaii, Nov. 12. Considered one of the toughest courses in the Marine Corps, both physically and mentally, the course teaches students to become water survival instructors. As an instructor, Marines learn to instruct and certify students in water survival. The course demands that students become proficient in various skills, such as swimming strokes, cardiopulmonary resuscitation and rescue techniques in the event of an emergency situation.