How to Map Sentinel 1 SAR and Sentinel 2 data to the same coordinate system?

Apply reproject from Raster tab —> Geometric Operations —> Reprojection

In snappy you could Reproject your data,

Take a look at this thread,

Source of the thread

And in python, nice example in here, Reproject Raster Data Python

Source : Redirecting…

It’s possible to create Shfile, within SNAP Or other sw, and then use it to subset your area of interest in this way, from Raster tab —> Mask —> LandSeaMask