Apply reproject from Raster tab —> Geometric Operations —> Reprojection
In snappy you could Reproject your data,
Take a look at this 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