Playa Blanca is without a doubt the most famous beach near Cartagena. As you may have guessed by the name, Playa Blanca is blessed with white sand beaches and crystalline water. It is located on Isla Baru but thanks to a recently added bridge, it is easily accessible from Cartagena by both land and sea which is great because the beach is also a jumping off point for excursions to the islands and for different water sports.
You can get there by taking a 40 minute boat ride from Cartagena or a two hour bus/colectivo ride. For the bus, you must first go to Pasacaballos and then take a colectivo to Playa Blanca from there. Although the overland trip takes longer than going by boat, you have the option to stay as many days as you want or come back later that evening after a biolilluminescence tour.