Simulation training has been an integral part of the military services for many years. Here the X9DI Trainer, nicknamed "Dumbo the Dunker," submerges with Marines on board to simulate a helicopter ditching at sea. This photo and other photos are available as prints from the Naval Institute Photo Archive. You may place orders or leave messages 24 hours a day at 1-800-233-8764, or contact [email protected], or visit our Web site, www.navalinstitute.org.