Cell service is at best spotty, and realistically, non-existent. On Santa Rosa Island, there are plenty of places where the park's radio net doesn't work. You are not able to trigger a repeater...

You are also dealing with variables like sea conditions and visibility (fog) which can change very quickly. Just because you can talk to the mainland doesn't mean you can reach the mainland.

Thereis an airstrip an dock on the developed portion of the island, but you can easily be a long day's walk (19-20 miles) distant.

If you are on the distant portions of the island, you need to have plans in case you have to spend the night out. This is one of the things that make working on the islnds so intriguing - you are close to civilizaation, yet very distant.