To get the app for free, download and install the Apple Store app from here. You should see the offer under the Store tab.
• Waterlogue transforms your photos into luminous watercolors.
• Watch Waterlogue paint as it transforms your images.
• Save you watercolors and share them on Instagram, Twitter, Facebook and Tumblr.
• Use your watercolors to create an artist’s journal or notebook.
• Create beautiful, high res, framable art for your home.
• Universal App for iPhone, iPad, and iPod touch.
• From the creator of Percolator and Popsicolor for iOS.
• 14 pre-set styles to customize your watercolors by controlling wetness, pen outlines and color.
• Image export at high resolution.
• Support for AirPrint.
• Control of borders, lightness, and detail.
• Includes example images.
Waterlogue is normally $2.99.