Melboune (Williamstown, just near docklands) to Geelong is the annual Geelong Week passage race! Its 34nm! In terms of time... that depends on wind direction, strength etc!
The bay can be a real challenge at times, wind can change quickly, and die out quickly. During this passage race this year I was on a Sprint750 tri! We had the kite up for the whole race, sometimes we were doing over 20kts, but in corio bay we parked for over an hour!
The best thing you could take on a journey like this is a second boat! Mobile phones work on the bay to!