Rarotonga is all about chilling out. Take the time to walk along the coral beaches - the water is crystal clear and so shallow you can walk on numerous little atolls and make like Robinson Caruso. The colors of the water are so fantastic, clearly divided by the reef into a lucent pale blue by the shore, the white of the waves crashing on the reef and then the dark blue of the ocean.
Quick Tips:
The water on Rarotonga hasn't been treated. This means it's drinkable and is drunk by all the locals who are used to it. It's up to you whether to chance it. Some people aren't affected, some are. If you do drink the local water and start to get stomach cramps, switch to bottled water right away and you should be okay.
My other BIG tip is watch out for the coral when you're paddling in the water. Wear beach sandals if you've got them otherwise you're likely to end up with cuts all over your feet. Also don't step on sea cucumbers - they won't hurt you, they're just the most disgusting things and squidge when you walk on them.
Best Way To Get Around:
The island isn't very big at all - you can walk all the way around it in about eight hours. On the other hand, unless you like very long walks, there are other forms of transport.
The Island bus goes all the way around clockwise and counter-clockwise, and costs .50 single or return. If you think you might be making a few trips you can get a strip of 10 journeys for . The alternatives are hiring a bicycle, about for the day, or a moped or car. If you choose the last two options you'll need to get a license from the Police Station in Avarua.
The choice is yours. There's really not that many places to go so most people travel either by bus or moped. Watch out for the local dogs though. Most of them make a game of trying to be run over by your bike.