The boat trip to the first island lasts more or less one hour. On the way you have the chance to see some fishing villages. In the picture you can see a floating house. It belongs to a local fisherman.
The boat will stop next to one of the islands, you will be given the snorkeling equipment. Make sure your mask is in good condition. If it is not, complain to your guide. Waters are warm all year round. The coral and the fish I saw were nothing exceptional, but I did enjoy the dive.