Advance
Ship's Penny
Ships are expensive to build and maintain. By imposing a ship's penny — a small tax levied on trade or port activities — we can ensure our fleet remains strong without draining our treasury.
Advance tree
The game files don’t say where this goes: it has no requires, so the game places it in the 
Discovery tree itself.
Modifiers
Definitionin_game/common/advances/4_choices_dip.txt:221
223icon = rudimentary_coastal_ship_repair
224for = dip