The John Gilman, a trawler out of Aberdeen, sets out on Friday. It's an unlucky day, but out they go, and run into a storm that nearly sinks them. In fact, they have to tell Wick Radio that they don't need salvage; that would mean they lose all their cargo.
The other IMDb commenter seems uncertain if Wick Radio was run by the British Post Office, which would make it a proper subject for the GPO's film unit. Perhaps the copy he looked at lacked the ending, which makes it clear that the PostOffice does run these stations, allowing the ships on the sea to keep in touch.
It's produced by Cavalcanti, and directed by Harry Watt, director of the classic documentary NIGHT MAIL. I see the roots of the sort of movie that Watt and others in his group would make during the War, showing Britons just doing their work under desperate situations.