The distance between Vung Tau and the Grand Ho Tram is about 30 miles. As far as I know, you need to be a guest at the Grand Ho Tram to use their bus service from HCMC. If you intend to use the hydrofoil service between HCMC and Vung Tau, be advised that the boarding location is no longer in District 1 (near the Majestic Hotel) but is now in District 4