The MV Chebu plies the Solomon and Bismark seas from Lae (departing every Sunday at 11am) to Buka (arrives Wednesday, seat/upper deck seat/1st class K420/K440/K650), via Kimbe (arrives Monday, K210/K222/K315) and Rabaul (arrives Tuesday, K320/340/420). The return voyage departs Buka on Wednesday, Rabaul on Thursday and Kimbe on Friday.
At the time of writing, the Buka service was only fortnightly; the ferry turning back from Rabaul to Kimbe and Lae, but keeping to the above schedule. Expect the schedule to change. The ticket office is off Bumbu Rd near the Lae Wharf.