Geremeas is a tourist village complex about 18km (about 24 minutes by car) from the ss554 ring road around Cagliari. Geremeas mainly consists of holiday homes and it has a three-kilometre-long beach and the beach is split by a river called riu Geremeas which is where the location gets its name.
The beaches are named Marongiu (Kal’e Moru) and Baccu Mandara.
The complex has a number of bars and restaurants, water sports and beach equipment hire and is generally very family friendly.
On a personal note, I have always preferred the eastern (Baccu Mandara) end of the beach because the sand is slightly courser, so although still very comfortable to sit or lay on, it easily falls off leaving you mostly sand free when you leave. Also, there is great snorkelling there.