Hong Kong Central from ShenZhen airport by ferry

Hello. There is ferry from shenzhen airport to Sky Pier in Hong Kong (near Hong Kong Airport). You need to take the ferry at 13:00. There is free bus in the airport taking you to Fuyong Pier where you can take the ferry, about 15 minutes at most. The cost for super class is 364 yuan and 272 for economy class. It takes about 50 minutes.
There is also shuttle bus runnning between. It departs time is 9:00-23:00 with 30 minutes interval. It is 180 yuan to get to Hong Kong international Airport and 90 yuan to get to Kowloon, i think you can get off at Kowloon.

There are 3 ferries in HK
And you can buy the ticket when you get there. There is Fu Yong Ferry Terminal, but you just can take in HK airport, maybe you can take a bus to Shenzhen airport, or take a boat to Shekou, it all depends on you

Boat is better but more expensive.