Go to Bannan Island in the Northwestern Sea and do the Romantic Fishing side quest. This involves a series of fishing quests given to you by the Old Wayfarer. Once you’ve completed them all, you’ll get a Heart Container.
The Traveler’s Ship
After you make it to the Northwestern Sea, you can visit a traveler’s ship called “the Prince of Red Lions”. Play the mini-game with the owner until you get a Heart Container.
After getting the Sun Key, head to Molida Island. There, get a score of 2000 points playing the Bow Shooting Range mini-game.
At the Northwestern Sea, win the Maze Island mini-game on Expert mode. You’ll have to complete the Beginner mode and Normal modes first, though.
Beedle’s Masked Ship
Purchase it from Beedle’s Masked Ship for 1500 rupees.
Can purchase from the Mercay Island teepee store after buying the Bombchu Bag.