Cozumel diving is drift diving: the current runs north along the island's leeward side and you go with it, over walls that drop into the channel. Palancar, Santa Rosa and Columbia are the names everyone knows, and the whole reef has been a national marine park since 1996, which is why it still looks the way it does.
This is a small Cozumel shop running those sites daily. The island's reefs suffered badly from stony coral tissue loss disease after 2018, and some sites are noticeably changed from older photographs — worth knowing before you compare what you see with what you were sold.