Playa Blanca is an excellent beach in the Caribbean coast of Colombia (20 km south of Cartagena) with classic tropical landscape - white sand and palm trees over water. A lot of people come here from Cartagena for the daily trip. But the beach is empty before 10am and after 4pm. Shore and seabed: sand. 
Fly to Cartagena International Airport (CTG). There are two main options to get from Cartagena to Playa Blanca. The first is by boat, the second is by bus + mototaxi. Both options cost about the same ($20 for the round-trip), but bus journey is more tedious and takes longer time.