If you fancy the underwaterworld. You can snorkel close to Ao Prao beach. You have to go to the left part of the bay. Swim about 5 minutes from the coast close to the cliffs.
There is some nice coral and many fish.
We saw many sea ergents (look out !!!) and a great Sea Horse. Also many coloured fish and beautiful coloured coral.
Equipment: You can hire snorkeling-equipment at the stand in front of the resort (on the beach).
You can contact a local tour operator in the island that caters Scuba diving and etc. There's the nearest small island off in Samet. Like Ko Khudee, Ko Talu that has pretty marine life. Though, I'm not allowed to dive after my Baby A. The operator told us that those islands has something to offer to.
Equipment: I've seen an operator that offers for rent equipments for scuba diving.
the nicest beaches are on the east coast. Starting from the north, here's selection of beaches I really liked: Ao Hin Khok, Ao Phai, Ao Phutsa, Ao Cho, Ao Wong Duen. Ao, you would have guessed it by now, means beach
Equipment: sun-block! i tried high-factor screen protection (protection 20) and within hours i got sunburnt
There are plenty of places where they will rent you a motorbike or a bike on the island. You can do it hourly or per 24 hours. I rented my motorbike from a more "private" person rather than the resorts and paid a little less, normally it is 300 baht per 24 hours. I got mine for 1000 baht for 5 days. Most of the places will not bargain with anybody, it is a set price (for foreigners anyways) across the whole island. If you care to save a couple bucks then check out all the places that you see.
Very handy with a motorbike i found, Our place was on Ao Cho beach and it was great to have the motorbike to go to 7-11 or the far east of the island to catch the sunsets.
Equipment: Make sure before renting the bikes that everything seems ok with it, and any problems found tell them so you do not get charged for it at the end.
As shown in the picture you will see people with snorkeling equipment on most of the beaches. It costs 50 Baht for everything and usually per hour. You can rent from either these people or check with your bungalow or resort.....most of the Guest Houses do offer snorkeling equipment. And most likely from your resort it will be cheaper.
When i rented mine from the Wonderland resort they didnt charge us just because we were staying there.
Equipment: Very basic snorkeling equipment.
To rent a Jet Ski on this island costs alot from what i heard. I never rented one my self however people told me that it has very high prices compared to other beaches around Thailand. A few of the beaches have the Jet Ski it on Ko Samet. Dont get me wrong, its not that expensive to rent them compared to the Western Countries, it just might be a little steep for a backpacker or a budget traveller.
You can also get pulled behind the boat on the banana for a few dollars.
Equipment: The equipment looked fairly new at all the renting places.
There is one place on Ko Samet from where you can rent a Quad. I am not sure about the cost of them but they were similar to the motobikes (a little bit more expensive). Available hourly or per day.