From A Wiki of Ice and Fire
Breakwater is built partially on huge, stone arches that stand as bulwarks against the sea. Entry to Breakwater is by a bridge of black basalt and a rusty iron portcullis. Its defenses include a deep salt moat and a drawbridge supported by two massive chains, followed by a larger gatehouse of algae-covered stones. Steps lead to Breakwater's cavernous stone keep. Its entrance is covered by threadbare Myrish carpet.
Breakwater's hall is gloomy and has a leaky roof. Only four of its twenty wall-mounted sconces hold torches. A white spider crab on a grey-green field, the sigil of House Borrell, is embroidered on a banner above the hall's hearth. Beneath the castle are dungeons.
During the War of the Usurper, Eddard Stark washed up on Sweetsister while trying to sail from the Vale of Arryn to the North to raise his banners. Lord Borrell, the father of Godric Borrell, could have turned Eddard over to King Aerys II for a reward, but instead freed him, saying, "If you lose, you were never here."