AdvanceChanged this version
Sheltered Ports
It is an unfortunate fact that ships tend to be damaged during battle, and equally unfortunate that the damage can rarely be repaired at sea. To alleviate this problem, we will create a system of sheltered ports along our coastline where our ships can patch themselves up.
Advance tree
The game files don’t say where this goes: it has no requires, so the game places it in the 
Absolutism tree itself.
Modifiers
Definitionin_game/common/advances/4_choices_dip.txt:374
376icon = rudimentary_coastal_ship_repair
377for = dip