Away from Home
Submariners spend the majority of their time underwater, meaning they have little to no contact with the outside world and news from home. This often means that they miss out on happy occasions such as graduations, births, etc.
Prior to embarking on another expedition, they write letters to their spouses or children, leaving something of them for the time they are gone. Some even order presents ahead of time for their loved ones in the event that they are unable to celebrate Christmas with them.