Ghostboat is a 2006 horror/thriller which originally aired on British television. It stars David Jason, whom I recognized immediately and with fondness from his portrayal of Frost in the Touch of Frost mystery series. Also here is Tony Haygarth (who was Renfield in the Frank Langella Dracula) and Julian Wadham (whom we recently saw in Outpost, and who has been on tv in Poirot, Miss Marple, Foyle's War and Inspector Lewis).
A WW2 submarine disappears and is assumed lost only to reappear in perfect condition -but sans crew- in the 1980s. The sole survivor of the WW2 crew (played by Jason) is prevailed on to join a mission to take the sub back to its last known 1940s location to try to discover what happened.
I can't find a trailer online anywhere, but you can watch the film at youtube. It originally aired on tv in 2 parts. Part 1 is here:
Moria calls it "an interesting genre item" and gives it a solid 3 stars. Reviews are not plentiful.