I worked with a guy who was in the Armed Guard (USN manning merchant deck guns.) When air raids started everyone went below decks except the Guard, manning the AA guns.
The guy said that in one raid with aircraft and U-Boats, the shop steward was the only civilian on deck, calling out the bonus money, running around yelling "bomb close aboard, that's $50!, torpedo wake, that's $100!" and so on. When the ship made harbor the crew passed the hat around. Sometimes the Guard made out pretty good, other times not a dime.
My dad worked at the Seaman's YMCA in NYC during the war (too old to get in). He spoke with a lot of skippers and crew who told of the horrific voyages they took - if you went into the water during the Murmansk runs you died in minutes from hypothermia, oilers burned you alive. One skipper told my dad that he always wore a life jacket - except when on an ore carrier or an ammo ship. The latter either sank like a rock or vaporized you when they were hit, so he just wore his jammies as he'd never get a chance to get off. Younger guys got in it for the money, but after one trip, if they survived, they went into the service where they felt safer.
All that being said, they were ably compensated and nobody drafted them into the Merchants.
My parish here in NJ has a memorial to one of our priest - Father John Washington - who was one of the Four Chaplains who died when their ship the Dorchester was torpedoed (off Greenland, I believe). They gave away their lifejackets to others on board, and were later honored with a US postage stamp.