There is considerable local boat traffic to and from Lindi's bustling port, but for travellers, Kilwa Kivinje, north of Lindi, is a better spot to try to arrange dhow travel along the coast.
All transport departs from the bus and taxi stand on Uhuru St. Minibuses to Mtwara (Tsh4000, three hours) depart daily between about 5.30am and 11am. Otherwise, there are minibuses throughout the day to Mingoyo junction (Mnazi Mmoja; Tsh2000), where you can wait for a Masasi–Mtwara bus.
To Masasi (Tsh5500, three to four hours), there are two or three direct buses daily, departing between about 6am and 10am. Alternatively, go to Mingoyo junction and wait for onward transport there. The last Mtwara–Masasi bus passes Mingoyo about 2pm.
To Dar es Salaam, there are direct buses daily, departing Lindi at about 5am (Tsh21,000, eight hours), and terminating at Mbagala Rangi Tatu transport stand in Dar es Salaam, which is also where you need to go to catch transport heading south to Lindi. Some lines terminate at Temeke.
To Kilwa Masoko, there’s at least one direct bus leaving Lindi daily by about 6am (Tsh7000, four hours).