HKIA to Shenzhen Airport in 2 hrs 20 mins ?

The ferry duration is about 45 mins. But I’m thinking that, it takes some time to complete the procedure after you arrival and before the next boarding. And the ferry schedule is not that dense, so no one can guarantee that you can get a ferry immediately on your arrival at the pier. Anyway, the time is rather tight and you are not recommended to book the connecting flight that early. BTW, passengers to take China domestic flights are usually advised to get to the airport 1.5-2 hours ahead of departure for boarding process.