The fleet of Stannis Baratheon sails into Blackwater Bay as a prelude to an attack on King's Landing. Tyrion Lannister destroys part of the fleet with wildfire, but this only manages to delay the landing of a significant number of Stannis' troops, triggering the Battle of the Blackwater.
In the books
In the A Song of Ice and Fire novels, Blackwater Bay is a fairly large body of water, held between the arms of Crackclaw Point to the north and Massey's Hook to the south, with the island of Dragonstone guarding the entrance to the bay. Elements of the King's Fleet patrol the Bay and ensure it is kept free from piracy.
Aside from King's Landing and Dragonstone, the largest port on the bay is Duskendale (which serves as a secondary port for King's Landing when the main port is overwhelmed with traffic), whilst the largest island is Driftmark, the seat of House Velaryon.
|Lord:||King Stannis Baratheon||Heir:||Princess Shireen Baratheon|
|Seat:||Dragonstone||Lands:||Blackwater Bay and the Stormlands|
|Title(s):||Lord of Dragonstone|
|Current members:||Queen Selyse Florent|
|Household:||Maester Cressen · Lady Melisandre · Ser Davos Seaworth · Ser Imry Florent · Matthos Seaworth · Bert|