- "Defying his mother's command, Rhaenyra's eldest son and heir, Jaecerys, mounted his dragon Vermax and flew to rescue his other brother and punish the enemy fleet. But the foolish boy let Vermax be hooked like a trout and dragged into the sea, where he soaked up even more arrows than seawater."
- ―Viserys Targaryen
At the beginning of the civil war the then Hand of the King Ser Otto Hightower had maintained a strategy mainly diplomatic to maintain isolated the side of the Blacks. However, when the husband of Rhaenyra Daemon took control of Harrenhal, the largest castle in Westeros and put the Riverlords on the side of his wife's claim, the young king Aegon was impatient with the strategy of his grandfather and deposed of his functions, replacing him by the Lord Commander of his Kingsguard Ser Criston Cole.
Shortly before leaving his functions of government, Ser Otto proposed as a last plan of his management agree an alliance with The Triarchy across the Narrow Sea, whom in the past won in a war against Daemon, but The Triarchy took a long time to receive the letter of Ser Otto and he had already deposed for when they acted.
Upon receiving the news of the death of Rhaenys, Rhaenyra entered panic, believing that a direct attack on her headquarters in Dragonstone was imminent she ordered her two youngest children, Aegon and Viserys ride their dragons and cross the Narrow Sea.
But when a few days after the children were flying over the Narrow Sea they were intercepted by the fleet of Triarchy surrounding Blackwater Bay. Prince Aegon was barely able to return alive to the coast of Dragonstone with his badly wounded dragon, while his younger brother had been captured by the enemy fleet.
Determined to rescue his brother, the eldest son of Rhaenyra Jacaerys defied the orders of his mother and rode his best dragon to face the Triarchy over the sea. But Jacaerys did not expect that the invading fleet was ready to face the dragons, and they caught his dragon with an arpon in its claw, forcing him to fly to the waves, where rider and dragon were exterminated.
The two continuous defeats suffered by the Blacks, in addition to the loss of her relatives, meant that Rhaenyra was losing too many of her dragons, which up to that moment seemed her greatest advantage. To make up for her losses, Rhaenyra reunited the bastard children of the Targaryen lodged in Dragonstone promising them great riches in exchange for they riding her dragons for her. They was known as the Dragonseeds.
Along with the death of Jacaerys, the battle meant the disappearance of Viseys Targaryen, the youngest son of Rhaenyra. No one knew for sure whether he was alive or not after the ambush. Aegon, the prince who survived the attack became since then the youngest son of Rhaenyra to whom she would be dedicated to protect personally until her death. After the war Aegon would become King of the Seven Kingdoms, and although his traumas made him a melancholy man, years after his coronation he discovered that his younger brother had not died but was kept as a hostage in the Free Cities, so he happily had to pay a ransom to return it to Westeros. Viserys would later become his brother's Hand, and eventually the successor of his sons on the throne.
In the books
House Velaryon blockaded the Gullet and controlled access to Blackwater Bay at the start of the civil war. After the assault on Harrenhal by Prince Daemon Targaryen and further blows to the greens, Ser Otto Hightower, the Hand of the King to Aegon II Targaryen, hatched a plan to break the Velaryon fleet's blockade. Otto reached out across the narrow sea to enemies of Prince Daemon, the Kingdom of the Three Daughters, hoping to persuade them to move against the Sea Snake, Lord Corlys Velaryon. Otto's plan took time and Aegon II eventually ran out of patience with his grandfather's prevarications, tearing the chain of office from his neck and tossing it to Ser Criston Cole.
However, the schemes of Ser Otto eventually bore fruit, as the High Council of the Triarchy accepted his offer of alliance in Tyrosh. Ninety warships, commanded by Admiral Sharako Lohar of Lys, swept from the Stepstones under the banners of the Three Daughters, bending their oars for the Gullet.
Meanwhile on Dragonstone, it was decided by Prince Jacaerys Velaryon that his half-brothers, Aegon and Viserys, would be fostered with a prince of Pentos until Rhaenys had secured the Iron Throne, they departed a Pentoshi cog, the Gay Abandon, towards the end of 129 AC. The Sea Snake sent seven of his warships with them as escort.
The Gay Abandon carrying the two Targaryen princes encountered the Three Daughters' fleet, which had sailed up to the Gullet. The Gay Abandon was taken captive and her escorts sunk or captured. Possessed only of a dragon egg, Prince Viserys had no way of escaping from the cog and was made captive.
Nine-year-old Aegon managed to escape the Gay Abandon by flying on his young dragon Stormcloud. Sailors attempted to bring them down and Stormcloud was wounded by arrows and scorpion bolts. Nevertheless, they managed to fly to Dragonstone, where Aegon delivered the news of the new threat from the east. Stormcloud at Dragonstone died from its wounds.
Flying on Vermax to meet the fleet of the Three Daughters, Prince Jacaerys swept down upon a line of Lysene galleys. The sailors had fought dragons during the War for the Stepstones, so their captains directed their spears and arrows against Jacaerys. One ship caught on fire and then another, however. When the dragons Silverwing, Sheepstealer, Seasmoke, and Vermithor joined Vermax from the Dragonmont, the line of Free Cities warships shattered as one galley after another turned away.
Vermax flew too low, however, and crashed down into the sea, possibly wounded from a crossbow bolt to the eye or pulled down by a grapnel. Survivors said he struggled in the rigging of a burning galley and sank with it. Jacaerys leapt free, but was killed by Myrish crossbowmen.
North and south of Dragonstone the battle raged into the night. The fleet bypassd Dragonstone, perhaps believing that it was to strong to assault, but they instead attacked Driftmark. Spicetown was brutally sacked, with its inhabitants butchered and left as carrion. High Tide and the treasures of Lord Corlys Velaryon were burned, with his servants cut down as they fled.
Thousands died from the battle, and Spicetown was never rebuilt. The Velaryon fleet lost almost a third of its strength. Prince Jacaerys Velaryon and his dragon Vermax were killed, and Prince Viserys Targaryen was taken captive.
The Triarchy's admiral, Sharako Lohar of Lys, took a combined fleet of 90 warships from the Stepstones but only 28 survived to limp home, losing 62 ships in the battle. The reaction of the Triarchy to such a hard won victory is unknown but by the time of Maiden's Day in 130 AC the Triarchy had begun to tear itself to pieces.