ZhuHai sits on the coast but also it forms the western shoreline of the Pearl river. Most big rivers, much like those in the US (Mississippi, etc.) are quite muddy, Brown and therefore considered “dirty”. Dirty as in muddy is not pretty but it is not to be mistaken for dirty as in polluted.
And yes muddy water is not much for a diver/snorkeler to have fun in.

If you travel a bit to the southwestern part of ZH either on the shore of HengQin Island or out towards the airport I think you will find the beaches there a little more to your liking and a little bit “cleaner” but then again there are many off-shoots of the Pearl that have outlets all down the Zhuhai coast.

Good luck, if you hunt down the shoreline a bit!

Are you still in Zhuhai? I am going to work there starting September 1st and I’d like to ask you some questions about local life.

Marie