what are the options to travel from Hong Kong, Shenzhen or Guangzhou to Beihai?

In Hong Kong, there is no direct bus to there, you need to take the MTR train to Shenzhen. Pass the immigration, you will find the Luohu Bus Station, where you can take a bus to the destination.

In Guangzhou South Railway Station, there are high-speed train to Beihai, you can take one.

Is there a flight from Hong Kong to BH?

There is no direct flight. You can take flight from HK to Nanning, and then transfer bus or train to reach.

thanks maggie

there are direct flights to hong kong by a few china airlines. About 300 to 1000 rmb