Uncharted Waters:
Don't be afraid to sail into uncharted areas of the sea. Many hidden islands and sparkling treasure spots are located off the main path. Use your sea chart to mark areas you want to explore later. Sometimes, sailing to the very edge of the map in a quadrant can reveal new landmasses.
Secret Passages:
In dungeons and on islands, always look for cracked walls that can be bombed, suspicious patches of ground that can be dug with the Shovel, or hidden switches that can be activated with the Boomerang or Bow. Many secrets, including Spirit Gems and Heart Containers, are hidden behind these environmental puzzles.
The Maze Island:
Beyond Beetle Island, there's another 'Maze Island' that features a more complex and challenging maze. Finding and completing this maze can yield some of the best rewards in the game, including rare ship parts and a significant amount of Rupees. Its location is often hinted at by NPCs or found on a Treasure Map.
Ghost Ship Clues:
The Ghost Ship's location changes, but NPCs on various islands often provide cryptic clues about its last known whereabouts. Pay attention to their dialogue and mark potential locations on your sea chart. Sometimes, the clue is a specific quadrant, other times it's a direction relative to an island.