One of my Uncles was on the Murmansk Run - the Russians treated them like the enemy. They were not allowed to leave ship after the horrendous trip though the Arctic Sea and attacks by the Germans. He never went on that run again. When he got back to the US, he joined the Coast Guard.
At one point and for quite a while, 50% of the ships making the Murmansk Run were sunk and in those cold waters all hand were lost with each sinking. Yet, knowing that, they still lined up to man those ships. I am in complete awe at that courage. I don't think I could have done it.
I heard that a lot of MM’s joined the Navy and Coast Guard after their tours because they couldn’t deal with being sitting ducks for the U-boats.