In this script, I create maps with Sentinel-3's OLCI, but can modify for a different ESA satellite.
ESA and NASA use different data structures. NASA stores all parameters in one NetCDF file, while ESA stores each parameter in a separate NetCDF.
Download M_map (https://www.eoas.ubc.ca/~rich/map.html) and move to functions folder. Store Sentinel-3 file folders in data folder.I recommending using getOC: https://github.com/OceanOptics/getOC It's a fantastic batch download tool.