The Griltjeplak is a large wet dune valley. Valleys in the dunes are referred to as "slab". The island name Griltje means beach plover. Griltjeplak is therefore the valley of the beach plover. This is a bird that likes to breed on barren beach plains. The Griltjeplak used to be such a beach plain in the past. This slice was created when a new strip of sand closed off the area from the sea. The Griltjeplak is now overgrown and the Kentish Plover has long ceased to breed there. Only the name still reminds of the bird. It is located on the west side of the island, near the Noordsvaarder.