Applied seascape ecology rests on paradigms of terrestrial landscape ecology. Patches defined by persistent seabed features are the basic units of analysis. Persistent oceanographic features provide context while dynamic features are usually ignored. Should seascape ecology rest on terrestrial paradigms? I use Reimann’s rules of analysis to identify differences between seascapes and landscapes. Reimann’s method uses hypotheses about system function to guide the development of models of system components based upon fundamental “laws”. The method forced me to avoid using terrestrial analogies in understanding of organism-habitat relationships. The fundamental laws applying to all organisms were the conservative metabolic requirements underlying individual performance and population growth. Physical properties of the environment; specifically those dictating strategies available to organisms meeting metabolic requirements, were the “laws” applying to the external environment. Organisms living in the ocean’s liquid meet most metabolic requirements using strong habitat selection for properties of the liquid that are controlled by “fast”, often episodic, atmospheric and tidal forces. Seascapes are therefor primarily driven by dynamic hydrography including mixing processes. In contrast, most terrestrial organisms are decoupled by gravity and physiological regulation from an atmospheric fluid that is metabolically more challenging. They show strong habitat selection for many essential metabolic materials concentrated on the land surface where slower biogeochemical processes including soil development drive ecological dynamics. Living in a liquid is different from living in a gas and resource use management in the oceans needs to be tuned to seascapes dynamics that is driven primarily by hydrodynamics and secondarily by seabed processes. Advances in ocean observing and data assimilative circulation models now permit the rapid development of applied seascape ecology. This development is essential now that changes in global climate are being rapidly translated into changes in the dynamics of the ocean hydrosphere that structures and controls ecological dynamics within seascapes.