Traditionally, rock cutting models for land-based and shallow water applications assume that the rock is cut under atmospheric and dry conditions. For deep sea applications this assumption is not valid, especially because the hydrostatic pressure can be of the same order of magnitude as the unconfined compressive strength of the rock. Therefore it is necessary that both the effect of hydrostatic pressure and the presence of a pore fluid are included in the rock cutting models as well. This paper focuses on extension of the existing phenomeno-logical rock cutting theory for deep sea applications. The suggested improvements of the model are based on observations from both experiments and simulations. The ideas presented can be helpful for the design of equipment for the drilling, deep sea mining and subsea trenching industries.