Not a marina. This is clearly a major oil terminal, with a sort of marina attached, mainly for local boatowners. Staff delightful, but the showers were in the local bar at 2 Euros a time (loos free, thank goodness). The town is very straightforward, but nothing to get excited about. We had hired a car from the local regional town (Sassari), so took the bus there to pick it up. Brilliant car. Peugeot estate, with 23km on the clock! Booked through Alamo, litteraly half the price of anything else. Ideal for collecting the family who arrive in dribs and drabs over the next couple of days.
After collecting our daughter from Olbia (4.5 hrs round trip), we decided to move on as there was so little in Porto Terres, and settled on Castelsardo. A straightforward 4 hr trip to the marina there.