Bocas del Toro is a group of islands in Panama, on the Caribbean side next to Costa Rica. Some are still very natural and pristine, some are more developed.
The main one is Isla Colon, which is full of restaurants, bars, and guesthouses, and where the airport is, along with all the boats to and from mainland and to the other islands. On the north side of Colon, away from the crowds, there is Bocas del Drago, a series of almost untouched beaches, right next to the rain forest, some of which famous for their sea stars population, to which I had the privilege to teach a yoga class! ;)
Isla Bastimento is also famous for its beautiful beaches, such as Wizard and Red Frog. On the other end the main town there is not very appealing and with no good swimming.
Isla Carenero is a good option because it has some nice beaches, it's very close to Bocas town but more quiet. Isla Zapatilla is a great day trip: classic tropical paradise and natural reserve.