You probably need a permit for those islands.

Probably. Most island parks (like Channel Islands, Isle Royale, or the Apostle Islands) require a separate permit or paid boat ticket on top of your general park entry fee.

The general entry fee gets you onto the mainland side. To actually set foot on the islands, you usually need a reservation for the ferry or private boat, and often a backcountry or day-use permit. Some islands also limit daily visitors to protect the ecosystem. Show up without planning, and you’ll be watching the boats leave without you.

Check the specific park’s page before you go. Rules vary, but “show up and wing it” is rarely an option for island access.

Plan ahead or stay on the dock.