Twice daily the privately owned, Osprey ferry makes a run from the tiny Grenadian Grenadine island of Petit Martinique to Carriacou and then on to Grenada. The Grenada to Carriacou portion takes about 1 1/2 hours, and completes a round trip, twice a day. If you fancy a quick day trip to Petit Martinique it's only a 20 min run from Carriacou.
The ferry is the most reasonable (though hardly cheap), and reliable way to go back and forth from Grenada to it's outlying islands. There are some flights into Carricou's Lauriston Airport from Pt. Salines in Grenada, but nowadays everyone seems to like traveling by ferry. It does arrive, after all, in St George's, eliminating the need for an expensive taxi ride from the airport.
And if you want a quick day trip to the 500 person strong island community of Petit Martinique, this is the way to do it.
If you want to traverse the entire chain of Islands you can begin your Grenadine island hop this way. Starting or finishing in Grenada. And from the other end begin or end in St Vincent. There are ferries all the way down and up the chain of islands, but it is difficult to hop the short distance from Union Island (St Vincent) to Carriacou (Grenada). Usually a very expensive private speedboat trip can bridge this gap.
Check their schedule:www.ospreylines.com
Grenada to Carriacou 9am and 5:30pm daily. M-F.Sat 9am only. Sunday 8am and 5:30pm
Carriacou to Grenada: 6am and 3:30pm daily. M-Sat. Sunday 3:30pm only
The cost: One Way from Grenada to Carriacou is $80 EC ($30US)