Great Keppel Island is the main reason many travelers stop in Yeppoon. Ferries run from Rosslyn Bay to an island of white beaches, clear water, walking tracks, and easy snorkelling on the Southern Great Barrier Reef. It feels more low-key than the Whitsundays, which is part of the appeal.
There are enough beaches to escape the arrival point if you are willing to walk, and the water can be excellent around sheltered coves. Go for the day if time is tight, but start early; the island deserves more than a rushed swim between ferry times.