Affter arrive at Macau Maritime ferry terminal, you can walk to visit the Fisherman's Wharf, then back to the ferry terminal to take the free shuttle bus to Lisboa casino, then walk to visit St. paul's Ruins and Senado Square. After that, you could catch a taxi to A-ma Temple and then go to Venetian to have a look if you have time. Anyway, you'd better catch a taxi for your tour in Macau since you only have half a day.