A School Trip to Yaeyama Islands

I thought I dreamed a dream of a southern island. I saw a white beach whose sand is like white powder. The beach descends to emerald-green shallows which is divided across with a white sandbar. Beyond them, there lies a brilliant blue sea. The gradation is just like a dream.
In the morning, I was in front of a washer. A pair of trousers had dirt of the island.
So it had not been a dream that I had been to southern islands as a school trip.