Marine energy, especially tidal current and ocean wave resources, bear immense potential for generating renewable power toward meeting global electricity needs. A number of conversion technologies have been successfully demonstrated worldwide and precommercial/commercial deployments are expected to appear in the near future. While electric power utilities foresee renewable technologies as a viable alternative to fossil fuels, marine energy technologies are generally excluded in their energy planning processes. Lack of technological preparedness and unavailability of device information are two major obstacles in that regard. This article provides an insight on how such novel schemes of power generation can be analyzed under conventional network planning exercises using generic information. The first study focuses on wave power integration along the coasts of Oregon, USA for the year 2019 and analyzes the Northwest electrical network. The second study considers both tidal current and ocean wave resources in South Korea for the years 2017 and 2022. The primary objective of these high-level grid scenario analysis is to identify the practical potential for longer term large-scale wave and/or tidal power generation, particularly focusing on the transmission networks. Steady-state (overloading and voltage deviations/collapses), time-domain (angular stability and dynamic voltage recovery characteristics), and small-signal (eigenvalue) stability analysis are carried out for these systems. Subsequent to establishing a number of study scenarios, N-1 contingencies and various suitable violation criteria are prepared, which are used in identifying the underlying network bottlenecks, especially within the coastal areas. Simplified generic dynamic models of tidal current and ocean wave devices are developed for the time-domain analysis. It is expected that similar studies, once conducted by the interested utilities, will equip them better toward considering marine energy in their future portfolios. In addition, device manufacturers and project developers will have greater confidence in the emerging marine energy market.