*a province where you have ships in adjacent waters. The Province Loot and Prestige will be transferred to the fleet, and will be added to your treasury when the fleet docks.
If you raid a province without either of the above requirements, you will
still get gold if you successfully siege down a holding and you can still get prisoners to ransom as well as artifacts.
For an army to raid, it must be set to a "raiding" stance before it leaves your territory. Armies can only enter this stance while you are at peace. As long as you remain at peace, looter armies only cost 10% maintenance.