Tolú is a quiet town three hours from Cartagena de Indias. This is a good place to take a trip to the Islands of San Bernardo. You can stay in one of the hotels, most of them are located in the promenade, and book the day trip in a nautic club. When you arrived to this city you must take a taxi-bike in order to go to the city center, but don´t expect a big downtown, there is only a church in the main square and a few streets arount it.
In my opinion, this islands are a better place to visit than the Rosario Islands in Cartagena. They are quieter and you go by boat with 12 or 14 people, then don´t think about big boats and crowds of people arriving to the island as in Cartagena, and I believe it is worth! The first island has a path to go for a walk with a guide, and you can see an original ecosistem in the middle of the nature,then there is an aquarium too to see some fishes, but the guide told us when the island belonged to Pablo Escobar there was a great investment of money, because he liked to have a nice place, but now there isn´t any money to keep it. After this island you take the boat again and go to the Múcura Island to have lunch some fish, like in everywhere in the Colombian coast, and enjoy a small beach. I decided to visit the rest of the island with a native and we went walking for 15 or 20 minutes, but you have to ask to somebody if you want to do this when you arrive to the island. You should give him a tip (about 2000 pesos) when you go back to the beach. It is worth because you can see some palm trees and banana trees.
If you have enogh time you can spend some days in Tolú and go to the nearby village of Coveñas, where you can find a better beach than in Tolú. It is only 15 minutes by bus, and buses are running very often, every 15 minutes.