It borrows from the Wind Waker concept of a world with a big ocean; with islands dotting the landscape. There will be some story in the form of Aryll, your sister and townspeople in your home town, Goron City and Zora Cave. After levels 1, 7 and 8, you can return to these towns and get new information out of them and get a new item from Aryll.
The game starts off on your home island and you MUST complete level 1 and then visit Aryll to get the raft so you can get off your island and explore the ocean. Now from here on in, you have free exploration through almost ALL the islands and areas of the huge 16x16 overworld. You can tackle levels 2-7 in any order you choose. With the small exception of gaining flippers from level 5 to access level 6. Other than that, you are free to go and do what you want and where you want. Just note that the further dungeons you skip to, the harder it will be on you since you may have fewer hearts early in the game.
Now as for secrets, here is a list:
- 2 HC Pieces on each major island
- 4 HC Pieces in 4 separate mini-dungeons found underwater in the vast ocean
- 6 Magic upgrades on 6 minor islands
- 8 Bomb upgrades on 8 major islands
- 3 Extra required dungeons including the new optional Master Dome
- Tons and Tons of rupees found on land, underwater, or found by defeating all enemies on certain overworld screens.
Enjoy!