Battle of the River Plate is one I've not seen mentioned. Managed to remain fairly factual - one of the most accurate ever made in terms of showing real naval procedure - and avoided steering into propaganda. Also had the remarkable feature of having HMNZS Achilles actually playing herself (though she was in the Indian navy by that point).
As an aside another notable element of Sink the Bismarck was that Esmond Knight played Captain Jack Leach on HMS Prince of Wales. Nothing exceptional in that, except that Knight served on Prince of Wales during the battle as a gunnery officer, and was very badly wounded, spending the rest of his life largely blind.
And if I'm going to mention naval films, then In Which We Serve was excellent, and the modern Master and Commander: The Far Side of the World was wonderful for different reasons. The latter is by far the most faithful depiction of the Age of Sail I've seen, and if they do insist on putting officers in dress uniform throughout, well I'll let them off.
