Possible Clues:

• Those who rarely put their head above water were part of major conflict in the sink business
• Turnabouts in vessels
• It's about wandering on small crafts, which once sunk a lot of resources into the sea perhaps
• WWII threats
• German submarines in WW2
• W.W. II threats
• Some subs
• Sinking ships?
• W.W. II wolf pack
• Subs supply to a sub