Reef

{Definition|title=Reef |definition= Reefs are hard mineral substrates such as rocks, till, or stones, primarily moraine ridges with block and stone cover in gravel/sandy surroundings, which rise mildly to prominently above the seafloor Threats_to_cold_water_coral_reefs,_sand_banks_and_seagrass_habitats_in_the_North_Sea_by_climate_change_effects:_sea_level_rise,_temperature_rise_and_storm_surges</ref>. }}