Is there alternative transportation at Public Ferries to join Hong Kong Airport from China Mainland?

Hello,
We are going to HK for a few days and we extend our stay at Dong'Ao Island (which is in Republic of China). We would like to know if there are some "taxi boat" or private boats that we can use to go directly from HK to Dong'Ao Island and then go back to HK Airport at the end of our stay?
Must we take the public ferry or there is other options ?
Thank you very much for your reply.
FP