This dataset contains sessile benthic coverage data derived from photographic quadrat samples collected in two time periods (2008–2009 and 2024) at two coastal sites in Northern Crete: Alykes (Heraklion) and Elounda Bay (Agios Nikolaos). Sampling was conducted along two transects per site at five depths (1 m, 5 m, 10 m, 15 m, and 20 m), using two quadrat sizes (25×25 cm and 100×100 cm) to capture replicate images. The data offer valuable insights into temporal shifts in sessile organism communities, highlighting changes potentially linked to climate change and the increasing presence of invasive herbivorous fish species, such as siganid fish and diademid sea urchins.