walking dogs off leash (Dar es Salaam)

Hello, Needing advice on places to walk our dogs OFF LEASH in or near Dar es Salaam. Is this even possible? We have two large dogs (golden retrievers) that require a lot of exercise and walking them on leash all the time will not allow them the exercise they need. Are there beaches with few people where we can let them run off leash? How do people exercise their large breed dogs in and around the city? Any advice is well appreciated!