Another big challenge was lack of proper protection. Unlike military ships, merchant vessels were not always armed. So they were easy targets. And yet, they had to keep sailing through dangerous waters to deliver supplies like fuel, food and ammunition to the Allied forces around the world.
The main challenge was the threat of enemy attacks, especially from U - boats. They could be torpedoed at any time.
Weather was also a huge problem. In some areas like the Arctic, they had to deal with freezing temperatures, icebergs and storms. Plus, they were often overloaded with supplies to meet the demands of the war, which made their ships less maneuverable.