Tidal notches can form on carbonate coasts during periods of relative stable sea-level, or when sea-level changes occur at a rate lower than the rate of bioerosion. Tidal notches have often been used for Quaternary sea-level reconstructions and for estimating tectonic movements, especially in uplifting areas. Underwater geomorphological survey may reveal evidence of submerged tidal notches. Detailed, accurate and systematic survey along the coastal zone by boat is necessary, to access all sites and establish lateral continuity of observation. During the survey, the local lithology is taken into account. For each site, the time and the GPS coordinates are collected. Underwater, the observed features are measured in relation to sea level and photographed. Notch geometries (height, vertex and inward depth) are measured and interpreted. The accuracy can be improved by multiple measurements and by corrections based on air pressure and tidal records. Submerged tidal notches cannot be dated directly, but their age can be inferred from coastal cores or archaeological data. Information on the duration of the various sea-level positions can be deduced from assumptions on the minimum and maximum values of intertidal bioerosion in carbonate rocks. Through this methodology new evidence concerning the rates of subsidence in the investigated area may be provided. The profiles of submerged notches, resulting from different combinations of RSL in sheltered areas,

allow to qualitatively distinguish the way of subsidence e.g. co-seismic event, gradual relative sea-level rise, etc. Some examples of tidal notch development and tectonic movements are provided from fossil submerged notches in Greece. Although tidal notches are not forming anymore in the present-day mid-littoral zone, underwater marks on carbonate cliffs may still provide evidence of submerged tidal notches corresponding to former sea level positions, or to recent vertical shoreline displacements of seismic origin.