All you need:
http://onthegreatsea.tumblr.com/DOWNLOADS
I tried this out in 4K last night and it looks glorious if you prefer the classic Gamecube look. I personally prefer the Wii U version and and Gamepad functionality, but this is a great way to revisit the game as well. Maybe I'll post some screenshots tonight.
Also, be sure to check the Dolphin Wiki pages for specific games in the future, they usually have this type of thing in the articles along with any issues, optimal settings, widescreen mods, etc. You can access these easily from within your Dolphin games library by right clicking the game and clicking "Wiki."
https://wiki.dolphin-emu.org/index.php?title=The_Legend_of_Zelda:_The_Wind_Waker
Wind Waker also uses a form of Depth of Field that works as intended at native resolution, but at higher internal resolutions it just makes things in the background look a bit soft and slightly blurry, nothing like actual DOF. There's an action replay code you can use to disable the effect entirely, it's in the wiki page. If you need help doing feel free to ask me.
I also recommend that you use
Ishiiruka instead of 5.0 or any of the official releases when using custom textures. It's an alternate unofficial branch of the main Dolphin with a number of added features. I was getting a lot of stuttering with the texture pack on 5.0 but on Ishiiruka it's very smooth. Maybe someone else can tell me why that is?