Assassins crees black flag help

[cjk]

hi guys
im like 11% through the game and i have a yellow ! witch means a new mission but it is in a part of the map i cant get to because my memory or somthing now im just sailing the sea
and ideas on what to do thanks ????

 

Go to the contemporary time zone, there's probably a mission there.

 

[cjk]

thanks man