Here are some potential research topics that combine oceanography and ArcGIS:

• Mapping ocean currents using drifter buoy data in ArcGIS - Analyze temporal and spatial patterns of currents. Integrate with ocean model output.
• Visualizing sea surface temperature data from satellites and in-situ sensors using ArcGIS - Look at trends and anomalies using time-series analysis.
• Ocean bathymetry mapping using GIS - Create high resolution maps by integrating depth soundings, satellite altimetry and mapping techniques.
• Analyzing coral reef habitats and topology with ArcGIS - Map and classify reef extent, health and biodiversity metrics using remote sensing.
• Site selection for offshore wind farms using GIS - Identify suitable areas based on bathymetry, ocean currents, infrastructure etc.
• Mapping marine protected areas and estimating habitat ranges of species using geospatial analysis.
• Identifying fishing zones and fish catch hot spots using vessel tracking data and GIS overlay analysis.
• Coastal erosion and shoreline change analysis using historic maps and coastal imagery in GIS.
• Tsunami propagation and flood modeling using digital elevation models in ArcGIS.
• Spatial analysis of beach water quality using microbes monitoring data for public health.
• Mapping ocean pollution from plastics using debris tracking and ocean circulation models.

The key is to leverage the spatial analysis and data visualization capabilities of GIS for ocean data. Choose topics where a geospatial approach can provide new insights. I am more inclined to use Gis combined with models. For example, machine learning models, deep learning models, species distribution models, etc.