Atlantic grey seals (Halichoerus grypus grypus) started recolonising Dutch coastal haul-outs in the 1950s, after practically 500 years of rarity in the Dutch coastal zone which was caused mainly by human hunting. The first pup-birth was recorded in 1985 at the Wadden Sea sandbank of Engelschhoek. Sandbanks in the Wadden Sea may form and recede in periods of decades, but may change abruptly as a result of a single storm. These rapidly evolving places are not the perfect breeding habitat for grey seals, which exhibit long-term fidelity to breeding sites and only reluctantly shift. Little is known of the geomorphology of the currently utilised pupping sites, nor the implications of change in structure on future occupation and selection of new sites.