Hamilton Island is the Whitsundays made easy: airport, marina, restaurants, pools, beaches, and tour desks all folded into one resort island. It is less wild than the national-park islands, but it is useful if you want reef access without the logistics of basing yourself in Airlie Beach.
The island works best for travellers who want comfort between boat trips. Walk up to Passage Peak for a proper view, swim at Catseye Beach when conditions are right, or use Hamilton as the launchpad for Whitehaven and outer-reef excursions.