Dar Es Salaam, Tanzania, is located right along the Indian Ocean, and while you can go to beaches at places in town like Coco Beach, it’s not really recommended to swim there (and not always the safest).
So one of the closest swimming beaches, which happens to be an island, is Bongoyo Island. Visiting the small island in the marine reserve, is one of the top things to do in Dar Es Salaam.
To get there you have to take a boat from the Slipway Center where you pay a fee for the day, board a boat, and they’ll deliver you to Bongoyo and bring you back at a later time.
The boat ride costs $20 per person (or the equivalent in Tanzanian Shillings), and the ride takes about 30 minutes.
The problem is that, they won’t depart unless there are 4 people or more. So if there’s not enough people for the 9:30 am departure, they won’t leave until 11:30 am (unless you pay more to accommodate 4 people) – can be a pain.