i saw in a Youtube video that they just made the set mako island but i think that the island is real but not the cave i am not 100% sure but go on Youtube and write in this.... H2o behind the scenes 2/3 and click on the first one and wewe will see oh and they do live in Australia
Mako (Shark) Island is a fictional island in the South Pacific Ocean au Coral Sea off the east coast of Australia. Mako Island is fictional and the girls live in Australia.