Taipa Ferry Terminal of Macau has boats to Shekou Port of Shenzhen at 11:15, 14:00 and 19:00. I am not sure if the 8 hours should reversed some part for the transportation from and back to Macau. You can get to see the Window of the World and China Spendid which are located next to each other. You can take Bus 70 and 113 from the port to the place.