A boat trip on Lake Tana is the one Bahir Dar experience you should not skip. Even a half-day route to the Zege Peninsula gives you waterbirds, fishermen, forest paths, and at least one monastery; longer trips reach quieter islands and feel more like a pilgrimage.
Before you leave, agree on the route, the number of stops, the return time, and whether monastery entry fees are included. The lake looks gentle, but distances are bigger than they appear from shore.