Being aboard ships for many years of your life, your legs have become comfortable and confident when you traverse difficult or uneven surfaces (ex. ropes, loose boards, narrow rooftops, or wet cobblestone). You have advantage on Acrobatics checks when maintaining your footing. 

Because you have fine turned your sense of direction and travel, you are able to intuitively make your way through new environments. You have advantage on Survival checks when navigating unfamiliar terrain (through alleyways, utilizing landmarks and your sense of direction to guide you).