This film is dire. It may well be "based on" a true story and a good one at that, but to make a film about a load of men singing tedious sea-shanties into anything interesting needs a good sub-story.
This doesn't have one - plots, coincidences, feelgood moments, sad moments are all somehow forced into the script wherever they can be, and are all totally predictable. Daniel Mays has a decent stab at pretending he enjoys the script, and Tuppence Middleton looks very pretty, but the rest is utter tosh