Waterway 
Buffer: 12.5%, Min Zoom Level: 4
Contains classes for rivers, stream, canal, drain, and ditch as line type. From zoom level 4 to 9, the data of waterway is from Natural Earth, and the zoom levels bigger than 10, the data is from OpenStreetMap. As for the Natural Earth data, the waterway layer are filtered by different types of data and the value of scale-rank.