From the airport, it's TOLL SR 836 "Dolphin Expressway" eastbound. When it crosses I-95 downtown, it becomes I-395 eastbound towards "Miami Beach". As the above poster mentioned, the tunnel is a LEFT exit and is signed as SR 887 "Port Miami". Once you come out of the tunnel on Dodge Island signs will tell you which terminal is home to your ship. Interestingly, in the opening of that video where the cameraman is on a highway with the ships across the water to his right, if you actually get that far, you've missed the tunnel and gone too far!