Isla Mocha is sparsely populated with rudimentary technology. Supplies, except for the basics, are hard to come by so plan ahead (bring sun screen!). The main industries here are fishing and animal husbandry.
The island was historically inhabited by the Mapuche peoples. The Mapuche believed that this island was the destination of the almas (souls) of the dead. It was frequented by pirates in the 18th and 19th centuries and it is believed that a sperm whale living near the island was the inspiration for Herman Melville's "Moby Dick."
The island has several coves, bays, docks and peninsulas around it. It is roughly ovular with large mountains jetting up in the center. A single road circumvents the island. The land is spotted with small farms and services such as stores, police, schools, and churches are found across the Eastern part of the island. The beaches are spectacular, with dunes and small seas formed with smaller islands.
 Flora and fauna
One will find many different types of livestock across the island as well as interesting birds. In the central mountains, there are small deer.
 Get in
Getting to Isla Mocha can prove difficult so plan ahead. The best way is to take a bus to Carahue from Cañete. Ask around about flights to the island, but beware that there are none on Sunday. The voyage by plane costs about $30 USD and takes 20 minutes or so. The people in Carahue and nearby Tirua are very kind so it may be possible to find your way there by private boat or to hitch a ride on the barge the goes out to the island semi-frequently.
Getting to the island by plane costs roughly $30 USD if you go from the airfield in Carahue. Getting to the from the airfield and the Carahue bus terminal can cost as little as $1 USD per person.
 Get around
On the island, the fastest way to get around besides walking is hitching a ride with a "carreton," which is a horse drawn buggy. Simply flag down a local and respectfully ask. They may or may not ask for money.
[add listing] See
You will want to circumvent the island. It can be done in one day if you move somewhat quickly (8-10 hours, est.). Along the way there are many scenic views, beautiful beaches, and other interesting sights, especially plants and animals. Also, if you have time, a hike up through the mountains will allow you to visit several beautiful lakes.
There was also quite a bit of damage done by the tsunami to the North Eastern part of the island. The ruins are quite interesting.
[add listing] Do
Hike. Beach. Interact with the kindly locals (but beware, the island accent is somewhat difficult to understand for non-native Spanish speakers).
[add listing] Eat
There are no restaurants on the island so be sure to bring food! There are three or four small stores on the island that sell basic food and drink. If you're lucky, you may get invited to dinner by the locals. Be sure to sample the various kinds of seafood that the fishermen of the island have to offer, if you get the chance.
[add listing] Drink
[add listing] Sleep
Do NOT sleep on the beach! During the recent tsunami, three Chilean hikers were swept out to sea while sleeping on the beach. You can pitch tent pretty much anywhere on the island. Be sure to ask the proprietors if you intend to set up camp in someone's field.
The entire place is back country! Explore the mountains or the Western part of the island!
 Stay safe
Do not sleep on the beach (see above). Be wary of the livestock: some of the larger animals are a bit agressive.
 Get out
Get out the way you got in! The easiest and most reliable way is to fly, but ask around and you may be able to find a ride by boat for significantly cheaper (but do not rely on this!). Once back on the mainland, take the bus up to Concepción or Santiago. If you're still in the adventuring spirit, go east through Temuco to Pucón where you'll find hiking, hot springs, volcanoes and all sorts of out door water sports. If you feel like island hopping, head down to Chiloé!