Most cruises kick off from Iquitos and It can be really easy to have there with direct flights from Lima. If you take one among the luxury cruises you can in fact start out from Nauta a historic port town ideal to the Marañón River - you will get there https://peru-jungle-tours-from-cu16048.smblogsites.com/33664187/the-best-jungle-tours-peru-diaries