The Isle of Cumbrae is accessable only by a Caledonian MacBrayne Ferry from Largs on the mainland.
The Isle itself is in the Forth of Clyde and has one town on it called Millport. It has a beautiful bay and tiny port, and can become quite busy in the summer months. Millport is very picturesque and a very friendly place to visit.
You have great views of Arran and the Forth of Clyde from the Isle of Cumbrae.