I've only been to two beach cities in China - Qingdao and Xiamen. Qingdao had a clean beach but it was the less popular one that was more off the beaten path. It actually looks really similar to the beach you went to. The other one was shockingly crowded and there was actually garbage floating in the water.

Xiamen was the same and I chose not to go swimming this time. It's a shame to see beaches get that dirty. Though what surprised me was the size of the garbage cans on the beaches. They had tiny little containers made to serve the thousands of people that frequent the beach. As you might expect, big piles began to form. Not the best sight to see at the beach!