If fossils of a water animal or plant are found in a place then that place used to be covered by water in the past.
Barnacles are animals that live in the water.
If fossils of barnacles are found in a place then that place used to be covered by water in the past.
what fossils have to be found in a place to signify the place used to be covered by water?

  bullfrogs
  Sediment
  Sea urchins
  dinosaurs
  barnacles
  humans
  patch reefs
  natural gas