I cant rave enough about Kennett River - between Lorne and Apollo Bay, at the beginning of Grey River Road, only 20m or so from the Caravan park entrance, several koalas often hang out in the low branches of the gum trees (only a metre or so above your head!)

Park at the caravan park and walk the road up and over the hill. Start bush bashing and keep your eye on the branches of the gum trees ahead. Dozens of koalas will be sleeping and eating amongst the Eucalypts. 

This will be the highlight of your Great Ocean Road experience.