晒太阳(shài tài yáng) - to sunbathe in Mandarin

晒太阳 (shài tàiyáng) means to sunbathe, built from 晒 (shài, to expose to the sun, to bask) and 太阳 (tàiyáng, the sun) as its object. Rather than a single verb like the English "sunbathe", Mandarin literally says "sun the sun", or more naturally, "bask in the sun".

晒 (shài) is a general verb for sun exposure, not limited to lying on a beach: 晒衣服 (shài yīfu) is "to hang washing out in the sun to dry", and 晒黑了 (shàihēi le) means "got a tan / got sunburnt", so the character itself just means "exposed to sunlight", with the object telling you what.

Because 晒太阳 (shài tàiyáng) is a verb-object pair, you can split it or add detail in between, for example 晒了一下午太阳 (shàile yí xiàwǔ tàiyáng), "sunbathed for a whole afternoon". It is common holiday vocabulary, often paired with 度假 (dùjià, to go on holiday) and 游泳 (yóuyǒng, to swim).