This application covers the needs for computational geophysical fluid dynamics and ocean modelling at the coastal oceanography group at Department of Marine Sciences at University of Gothenburg. Physical oceanography is a discipline that is a traditional user of supercomputing resources, as it involves solving large partial differential equation systems. This application is a direct continuation from a line of SNIC/NAISS projects. The project will include several oceanographic applications ranging from 10 m scales to 100 km scales. Thus, different models will be used for different projects and will be described in this application. All applications are based on well-developed codes with a large international user groups, all of them being already installed and run on the supercomputer Tetralith. All applications have been developed with HPC resources in mind. More specific we consider investigations on: • Tidal energy is an emerging sustainable power source. In order to increase the extractable amount, the power plants need to be arranged in farms as for wind power (PhD work). Here the turbulence in a tidal current and how it impacts on Deep Green, which is a tidal energy extracting device developed by Swedish company Minesto. This is a continuation on a previous large-scale project but will end in autumn 2025. Part of this work will use GPU resources. • Regional oceanography in Skagerrak on the Swedish west coast. We will investigate the properties of the Skagerrak using two ships (one Swedish ship and one German ship) in September 2025. To make the most of the measurements we will also look models for the time of the observations. Here we (probably) use an earlier model set up using the Regional ocean Models System (ROMS) that was used in a publication in 2024. • Regional oceanography in Öresund on the Swedish west coast. The studies include how larvae of invasive species Pacific oyster are transported by currents (manuscript in progress). The transport of e.g. E. Coli bacteria toward beaches in Helsingborg Municipality will also be investigated (project that is starting up). • We will use a high-resolution setup (450 m resolution) for the Baltic Sea to investigate how subsurface currents can be derived from surface currents. The application is to use remote sensing products to evaluate currents in the Baltic Sea. The model is used as a test bed of the theoretical method required to derive ocean currents from remote sensing products. Parts of developed methodology need to be reevaluated for usage in the Baltic Sea. • Resources will also be allocated depending on the needs to Master students (presently 1 students) that would carry out a short internship or thesis during the project period.