Complex sentence: The visibility, especially in early summer, is good and can be up to 20 m. The seabed consists of mostly infertile sand that reflects much of the sunlight from the surface, aiding the surveying and documentation of the site with underwater cameras.
Split into simpler sentences: The visibility, especially in early summer, is good and can be up to 20 m. The seabed consists of mostly infertile sand, which reflects much of sunlight from the surface. This factor has greatly helped the surveying and documentation of the site with underwater cameras.