Where is the water surface, and where is the sky, everything has mergedWhere is the water surface, and where is the sky, everything has merged
Boats on the sea surface in the light of the setting sunBoats on the sea surface in the light of the setting sun
В математике: граница, отделяющая геометрическое тело от внешнего пространства. Наружная сторона чего-н..