I find myself thinking often about plastics and our impact, in general, on the world out here. The beaches of paradise are littered with plastics. Even remote Suwarrow would yield a few garbage bags full from the small beaches on the main island.
So is it possible to cruise without using plastics? It would certainly reduce our dependence on fossil fuels to do so, but without a huge effort, I think it is not feasible. Too many things we take for granted are made from plastic.
Starting with the boat, we would have to build one from some other material other than fiberglass, which is plastic resin reinforced by glass fibers. Our running rigging would have to be replaced with wood or metal blocks and lines made from natural materials such as hemp or sisal. We would forego electricity on board, because wires and connectors use plastic for insulation and almost all electrical devices are made at least in part from plastic, valuable for its insulating qualities. Reverting to cloth covered wire and wooden/metal appliances might be possible, but the results would be unlikely to hold up in a wet, salty environment. Without electricity, we lose our depth sounder, GPS, and lighting. The latter would need to be done entirely with kerosene and would require lanterns for the running lights (two or three), anchor light, and interior lights. We would have no engine, since the pipes that feed water and the many of gaskets that seal it are made of plastics. Plumbing would also have to be re-done with metal pipes only, sealed with lead or oakum joints. We would have to look long and hard to find a metal compass to navigate by and an all metal sextant for off-shore work. Our chronometer would also need to be all-metal and glass - hand wound. I suspect a 'simple' non-plastic boat would cost more to build and be a pain to maintain.
Re-provisioning would be possible, but difficult, without plastic, since most processed 'foods' are packaged in plastic. We would bring cloth bags to the local market and have to be very choosy as to what we bought in the grocery store. Perhaps this is where we can have the most impact - by buying fewer plastic containers, especially out here in places like Tonga, where most plastic is simply thrown on the ground, burned, or dumped in the ocean.