FPSOs are commonly proposed and used for offshore oil production. Due to the fundamental requirement of FPSOs to remain moored at their location, they are unable to avoid severe weather. FPSOs normally operate head to the weather, and sensitive equipment located near the bow will be susceptible to green water damage. Damage may occur to both equipment and superstructure, with resulting risk to personnel. To initially access green water is allowed by the physical understanding of green water events. In this paper the main focus is put on the physical phenomena of green water accounted for with the tested data in regular waves.