Tidal flats are areas on or near the coast that are covered during high tide and exposed during low tide. These are generally muddy or sandy areas. In fictional worlds they may be expansive, and unwary characters may find themselves unluckily caught when the tide returns. Ships may equally find themselves in dire circumstances when the tide goes out. They may also offer a land-based means to travel from one coastal region to another nearby island or landmass (depending on the tides), similar to a land bridge. During low tide, structures, buildings, fossils, giant skeletons, ruins, and wrecks may all be exposed.