from hk airport to guangzhou(canton fair) by ferry.prices also.

Only one ferry is scheduled between Skypier, HKIA and Guangzhou Nansha Port leaving at 11:15. Upon your arrival at Nansha Port, you can take the free shuttle bus to Jiaomen MTR Station, where transfer to local subway line 4 to Wanshengwei. Then transfer to line 8 to Pazhou Station, from which walk to Canton Fair sites.

It costs CNY310 (356HKD) for the economy class cabin and CNY265 (304HKD) per person. However, as I know, the ferry is only in operation every Tue. Thur. and Sat. You'd better further confirm that!