How do you fill a bottle in Skyward Sword? I'm trying to scoop up some water, and I can't figure out how to get the bottle equipped.
Just to clarify: to equip items, you have to press - (minus) when you're on the main walking-around screen, not when you're on the inventory screen (which you can separately access by pressing 1 [one]). It's confusing because there is also a pouch in the middle of the inventory, which you can also interact with using the - (minus) button.
Hold - then mouseover the desired item to equip (shield or bottle; medals are considered equipped if Link is carrying one and bags provide a passive storage bonus). Note that you don't have to equip a bottle to catch a fairy, you can use the Bug Catching Net instead.
To scoop up water, equip a bottle then press A while standing in the water.