the shrine/grave looks fairly new to me, but the wording on the grave suggests whoever buried here died more than 100 years ago. It is probably housing an ancestor of the people living on the island.

Paper money is usually burned during visits to the grave. It's believed that the paper money is "transferred" to hell after burning to ash. The paper money put under the rocks is to show other people that the villagers have heart and have done their job to pay visit.

you might ask why do I know these things, cos I am from Hong Kong :)