I've never seen a sub film festival, but can certainly suggest a few movies - some directly sub-related, some tangentially, some to stay FAR FAR AWAY from.
Run Silent, Run Deep - Clarke Gable and Burt Lancaster - great WWII fleet boat scenes, good drama, some glimpses into life among the crew.
Das Boot - Best U-Boat movie around. Hard to watch, the crew goes thru so, so much in 2 1/2 hours of submarine claustrophobia.
U-571 - STAY AWAY! That's all I'll say. Instead see:
Enigma - Fictionalized life of Bletchley Park and British code breaking of the German Enigma machine, especially with regard to breaking the "Shark" U-boat cipher. Some surfaced U-boat scenes.
Ice Station Zebra - Said to be Howard Hughes favorite film - Rock Hudson, Patrick McGoonan, Ernest Borgnine and Jim Brown all on a nuclear submarine all trying to get a Russian spy satellite landed near the North Pole.
The Hunt for Red October - Sean Connery and VERY YOUNG Alex Baldwin - my ex-navy nukes I work with can find a few things terribly wrong with it, but its awfully entertaining. Besides, Tim Curry of The Rocky Horror Picture Show playing a Russian doctor??? Amazing!
Finally, in War and Remembrance there are many scenes of Pacific Fleet subs throughout the gazillion-part mini-series. They used Bowfin out of Hawaii in the filming.
Jay Boggess