Wearing certain outfits will give you helpful abilities in Hello Kitty Island Adventure. One example is the Mermaid Outfit, which slightly boosts your swim speed and reduces the cost of stamina when diving. Equipping all three pieces of the outfit will enhance these effects. However, swapping between outfits each time your character dips into the water can be tedious. You'll need to pause and change clothes manually. Luckily, there's a way to auto-equip the Mermaid Outfit, and that's by completing the "Mermaidified Fashion" quest.