Jag antar att det är det enda sättet.
Från annan webbplats:
Visiting Idjwi Island is super-easy from either Goma or Bukavu-- and is highly highly recommended, for a peaceful, friendly and very scenic island.
Ytterligare information:
Boats from either Goma or Bukavu are plentiful-- either take the MV Mugote, or MV Emmanuel (not Emmanuel 2), or MV Iko (though this one really looks like it's on its last legs). There are plenty of other boats going between Goma and Bukavu but they don't stop on Idjwi. Fares are about $15 for first-class from either Goma or Bukavu, and takes 3-4 hours from Goma and 2-3 hours from Bukavu.
Eftersom 2 officiella webbplatser ger informationen jag skulle lita på det.