The marine mammals website (www.marinemammals.be) in its current form is the result of a long-standing collaboration between RBINS and the University of Liège and provides access to data from 50 years of marine mammal observations in Belgium. The database that backs it consists of two parts, i.e. observations and information on necropsied tissues and subsequent diagnoses on the cause of the death of the animal. The database records all stranding events in Belgium from recent years. The dataset provides the occurrences and associated data like putative circumstances and putative cause of death.