Standing before an enormous seascape, the speaker feels himself expand to match it. He addresses the scene directly, as if sky, sand, and sea are a living presence he can answer. The repeated colors—blue sky, brown sand, blue sea—create a simple, almost chant-like rhythm. He wants to run along the endless beach, shout at the breaking spray, and touch the sky with his fingers, as if the landscape gives him unlimited energy and freedom. The mood is bright and exultant, full of physical joy.
Then the final lines shift slightly. His happiness is like sand held in his hand: he lets it run out. That image suggests happiness is not something to grip or keep. It is vivid and real, but also fleeting. The speaker doesn't treat that as a tragedy. He enjoys the feeling fully while it lasts, accepting that it will slip away like grains of sand.