qiánshuǐ / shí / chūxuézhě / kěyǐ / shǐyòng / hūxīguǎn / zài / shuǐmiàn / huànqì潜水时,初学者可以使用呼吸管在水面换气。When diving, beginners can use a snorkel to breathe at the water surface.