参考答案

正确答案：B
解析：细节题。第一段When he was so far out that he could look back not only on the little bay hut past the stretch of rock that was between it and the seashore，he floated on the warm surface and looked for his mother．通过这句话可知，当他游得很远时，他回头不仅可以看见小海滩，而且跨过海滩还可以看到其中的岩石和海滨，他漂浮在水中，并寻找着他的母亲。所以，答案是B。