Our embarkation was in Guadeloupe which does not give you many options from Canada. But learning that it is a French island flights from Montreal are direct and worth going.
Costa did not offer transfers from airport to ship but a taxi ride was 20. Euro and if you can share it's a good deal.
I did not explore Guadeloupe as much as I wished, perhaps next time, the taxi ride from the airport to the ship was easy and I was able to connect to others going my way to share a ride. Embarkation was smooth enough although we had to wait because they would not let us on until 3:00 pm so we waited an hour or so.