Depends on what location you are travelling to and how fast the boat is, you can reach the Great Barrier Reef in 45 minutes but most boats travel to the outer reef which it can take up to 2 hours to get there.
The islands (Fitzroy Island & Green Island) are a bit closer to the main land taking an average of 45 minutes to get there. The reef is located around the island and you snorkel from the beach which it is an easy and comfortable experience but the islands are considered the inner reef . Most people who come to Cairns wants to visit the Outer Reef which is considered a better quality reef. It takes an average time of 1 hour and 30 minutes from Cairns marina to get to the outer reef depending on location and boat type.
Have a look at our “Tour Overview” of each tour page to find out travelling time and time of departure and return.