Advance
The Western Shore
For millennia we have fished, traded, and fought along the wild Atlantic coasts. From these harsh waters, we have learned seamanship unmatched by any rival.
CelticaFormable CountrypotentialAdvance tree
The game files don’t say where this goes: it has no requires, so the game places it in the 
Renaissance tree itself.
Modifiers
Light Ship Power+10%
Definitionin_game/common/advances/culture_irish.txt:197
200icon = nav_fearless_seamen