Nakajima's Island by Joseph H. Stephens

In 1944, the world's largest submarine was completely unknown to the Allies in the Pacific. At 400 feet in length and carrying three dive bomber/float planes along with massive cargo capacity, the I-400 was the Imperial Japanese Navy's top secret weapon. Its intended use was to bomb the locks of the Panama Canal and to drop containers of rats infected with bubonic plague on American cities. By 1944 however, the war had taken a turn for the worse for Imperial Japan. Out of desperation, the I-400 was used instead as a transport vessel. In this work of historical fiction, its last task was to transport the stolen Dutch National Treasury from Jakarta, Dutch East Indies to the Truk Mandated Islands. Instead, it ended up being bombed and sunk in the lagoon of an uncharted island among the hundreds in Micronesia. The only survivor of the sinking, a Major in the Imperial Japanese Army Air Force, Hiro Nakajima, was assigned to escort the secret cargo. Hiro kept his secrets for decades. Until now.