The bus ticket office outside Bremerhaven’s train station has free maps of town, as do the tourist offices. Within Bremerhaven, single bus tickets/day passes cost €2.50/7.10. From the train station, buses 502, 506 and 509 stop at Havenwelten, near the Alter Hafen (Old Harbour) and Neuer Hafen (New Harbour). Buses 505 and 506 go to Schaufenster Fischereihafen, in the other direction.
You can rent out bicycles (regular/e-bike per day €8/25) from both the main tourist office at Neue Hafen and the branch at the fishing harbour.