The Corsair fleet seems to be attacking multiple key locations simultaneously. To stop the attack, you must defend Dol Amroth from the Corsair ships.

When Revealed: Search the encounter deck and discard pile for a Ship enemy and add it to the staging area (2 Ship enemies instead if there are 3 or 4 players in the game). Shuffle the encounter deck. For each unguarded objective in the staging area, attach a non-unique Ship enemy in the staging area to that objective, guarding it.

Sailing.

If your current heading is at the worst setting (Stormy), Raider Flagship gets -50 engagement cost.

You cannot advance while at least 1 objective is guarded by an encounter.