Hi. My wife are travelers and lived in Malta for 8 months. We lived in Vittoriosa, better known as Birgu to the locals and people like us who lived there. With an 8a-6p timeline I would get off the ship and right there you will find those cool colored little skiffs that will take you over to Birgu for a couple of euros per person, or also right there you can get on the ferry for about 4 euros. Either way its no more than a 10 minute ride. You will go by billionaire (think Russian) and millionaire yacht row. Beautiful boats to see up close. We lived in St. Angelo Mansions right beside Ft. Saint Angelo used by the Knights of St. John to fight off the Ottoman Turks in the 1500's. The town of Birgu is not large but does have some wonderful scenery.
From there I would get back on the ferry or skiff and head to the elevator that will not be crowded by the time you get back after seeing Birgu (it can be a 20-30 minute wait with the rush of passengers). The elevator will take you from the water up to Valletta. From there you will find the main bus depot if you go more left where you can catch a 30 minute ride Mdina (a must see and former capital of Malta centuries ago.) It is a walled town and is an excellent place to visit. From there I would go back to Valletta. This two place experience will take about 4 hours but well worth it. After that you can do some of the suggested water activities but honestly we're more into the history of the island so we didn't get much out of that. Valletta itself is a worthy 2 to 2.5 hours. Walk down the main street, 'Triq Republic'. Its a tourist walk but halfway down you pass the courthouse with a large outdoor Cafe. there are also several museums of medium size that house a great deal of Malta's history up to and including WW2. Have fun!
