During WWII, as the silhouette of the submarine conning towers changed, so did the deck layout. The Nautilus Lionfish deck series covers five important deck variations in the war. The principle changes in the deck layout concerned the under-deck stowage of whaleboats and the locations of access points to the superstructure as well as minor items as air salvage ports and deck equipment locations. I have listed the decks here in their chronological order. All of these decks were drawn from US Navy blueprints found in the National Archives. This deck is designed to match the first of the Gato class as commissioned in 1941. The deck includes locations for two whaleboats abeam of the forward gun foundation. This deck also had numerous maintenance points along the deck to provide access to hull fittings and such.