The Phantom Submarine (1940)

On the night before he sails in search of the steamship Arcadia's sunken gold, Paul Sinclair (Bruce Bennett) meets Madeleine Neilson (Anita Louise) in a San Francisco nightclub. On the second day at sea, Madeleine turns up as a stowaway. While diving and searching for the sunken gold off the Philippines, Paul discovers that a foreign submarine has been laying mines in order to completely cut off the Philippines from American protection.