Large cruise ships carrying hundreds of passengers aren't allowed because they would overrun visitor sites. Five small vessels were in the harbor, formed by an extinct volcano's crater, when we arrived. But we had some other islands all to ourselves. Ashore, visitors take nature walks, not hikes. You don't cover any great distance and, except for a climb up a volcanic cone on Bartolome, most are easy walks.
Visitors usually stay within sight of the shore.
All are escorted by naturalists and move slowly, admiring wildlife and learning to appreciate this fragile environment. In most places you must stay on trails marked with white stakes. No litter, not even footprints, are beyond those trails. Visitors can wander more on some beaches. Some are gritty black sand, others red sand, others great fractured sheets of black lava with natural bridges carved by pounding surf.